Several months ago I wrote a piece entitled "10 Types of Superhero Successors" (linked at the bottom of this piece.) The mission statement was to list all the rationales I've seen different writers use for having a "new guy" step forward to replace an "old guy" in the superhero racket while recycling the same heroic alias. Only later did it occur to me that I might also want to attack the subject from a different angle by examining all the different excuses that can be employed to give the "old guy" the boot. Sometimes it is blatantly obvious that this is done just to create a "sudden vacancy" for a "new guy" to fill, but sometimes there are other factors at work! Whatever the exact motive may be in each case, I chose to write down examples of all the different reasons I've seen writers use to justify the sudden disappearance from the scene of a veteran hero.
Naturally I'm going to mention several "Elseworlds" stories (or the functional equivalents, such as "this is one possible future timeline, but it's not set in stone") to illustrate my points. Over the years, various writers have wanted to tell us about the "end of Superman" or the "end of Batman" or whatever, and of course they know perfectly well they can't do that and make it stick in "regular continuity" when those cash cows are expected to keep having adventures and earning money for their owners. They could try, but then they (or their successors) would just be ordered to find a way to bring back the temporarily-absent hero so he could star in his own title (or titles) again.
Accordingly, a clever writer who wants to do such a story often gets permission to do it in stories that are set in their own crazy little timelines instead, so they'll have no binding effect on anybody's "regular ongoing continuity"! This reasoning certainly applies to Batman's lengthy retirement and return to active duty in Frank Miller's "Batman: The Dark Knight Returns." In the mid-90s, when a "Tenth Anniversary Edition" of it was being released, I believe I saw a DC editor quoted as saying (loosely paraphrased from my imperfect memory): "The only reason 'Dark Knight Returns' didn't have the Elseworlds logo on the cover when it was first published is because we hadn't even invented the Elseworlds logo yet! But if it were being released today for the first time, you'd better believe it would be labelled that way! It was never intended to 'guarantee' anything about a predestined future for Batman!" (Or words to that general effect.)
13 Reasons to Quit the Superhero Racket
01. Death02. Maiming03. Marriage and Family Responsibilities04. Power Loss05. Burnout06. Disgraced07. Imprisoned08. Outlawed09. Cashing In10. Quitting Your Job (or Being Fired)11. Missing in Action 12. New Paint Job13. Turning to the Dark Side of the Force
"I'd love to help save the world again, except that I just got killed. You'll have to go this one without me!"
This has been done many, many times. Sometimes the corpse is barely in the coffin before a Successor steps up to bat, using the same superhero name. I've seen many complaints about this in connection with the recent death of one Blue Beetle (Ted Kord) just before a teenager named Jaime Reyes got magically endowed with certain powers which let him become the newest Blue Beetle during "Infinite Crisis." Similarly, Ronnie Raymond (Firestorm) died suddenly in "Identity Crisis" and then Jason Rusch abruptly became the new Firestorm.
But if we look at it a little differently: "Death" for a superhero just seems to mean "I'm taking a vacation to get a well-deserved rest before I miraculously return and get back to work!" This is particularly true in the X-Men titles, but it also happened with Superman in 1992-1993. He died fighting Doomsday; he got a nice funeral; four other guys all popped up wearing S-shields on their chests (and three out of four explicitly laid claim to the name Superman); then the real Superman bounded back to center stage in his own titles after a nice rest! I never seriously expected Superman's death to last very long, but he was unquestionably "absent from the scene" for a while there!
"I'd love to keep fighting, but I'm physically incapable of maintaining the superhero lifestyle."
Bruce Wayne found it necessary to abandon the role of Batman for about a year (our time -- a lot less from his perspective) after Bane broke his back in "Knightfall."
His friend Barbara Gordon, of course, had suffered similar injuries several years earlier, which ended her career as the first Batgirl -- and unlike Bruce, she never got a Psychic Miracle Cure to put her back on her feet, good as new!
And of course John Stewart has been put in a wheelchair, put back on his feet, put back in the wheelchair, put back on his feet. . . .
03. Marriage and Family Responsibilities
"Fighting ruthless supervillains several times a week was all very well and good when I was a carefree bachelor, but now it's time for me to grow up and concentrate on my new family responsibilities instead."
Some heroes seem to feel that "regular superheroics" and "being a good spouse (and/or a good parent)" are mutually exclusive concepts. I believe this has been stated or implied in the cases of various Golden Age heroes, at one company or another, who faded into limbo (as far as real-world publishing history is concerned) after World War II ended and the first "boom" in the superhero industry came to a crashing halt. Later stories would establish that many of those characters had married their sweethearts and settled down to live the American dream, while raising kids and trying to get promoted in their regular occupations and all that fun stuff.
On a similar note: In the MC2 timeline, a key part of the backstory is that many years before Peter Parker's daughter started calling herself Spider-Girl, Peter had finally quit being Spider-Man for reasons that amounted to a combination of #2 and #3. Losing one leg in his final battle with Norman Osborn (the original Green Goblin) constituted a wake-up call to him; he decided it was a strong sign that he should quit while he was ahead and make sure to spend plenty of time with his baby daughter as she grew up. This despite Mister Fantastic's ideas for a state-of-the-art artificial leg that would let him continue to easily climb walls, make those superhumanly strong leaps across streets, and so forth.
(Of course, I should note that in real life, many people serve in combat arms of a military service, or as cops, or in other risky occupations, and yet go right ahead and get married and raise children at the same time.)
04. Power Loss
"I wanted to stay in the game, but I just lost my principal qualifications."
The difference from "Maiming" is that here the hero may still be in superb health by any "normal" standard, but no longer has that extra edge he was always accustomed to rely upon in life-and-death situations.
This can cover such things as "loss of biological-based powers" or "loss of special equipment that bestowed great power when worn."
As a recent (and temporary) example: In the "Up, Up, and Away" eight-part story arc that ran in two titles last year, set "One Year Later" after "Infinite Crisis" had been over and done with for twelve months from the DCU's point of view, we learned quickly that Superman's powers had faded away for some reason around the time the "Infinite Crisis" ended, and he had spent the past year adjusting very well to a non-superheroic lifestyle as plain old Clark Kent; working full-time to be a Daily Planet reporter and Lois Lane's loving husband, and apparently giving tips to his cousin Supergirl as she filled his boots as the foremost superpowered guardian of Metropolis whenever another villain went on a rampage. (Which seems to be an hourly occurrence in that town.)
Another good example would be what happened (or apparently happened) to Richard Rider after his series "The Man Called Nova" was cancelled in 1979. But that also fits under another category, so I'll discuss it further under Reason #10.
"Friends -- I just can't take it any more. Not right now, anyway. I want to find some nice quiet little corner of the world and get reacquainted with how normal people live. I might come back later -- but don't hold your breath."
The psychological wear and tear of long periods of facing depraved villainy can be considerable. Some heroes get overwhelmed after a while.
To offer some perspective: I once read that psychologists and physicians studying the U.S. Army during both World Wars reached the conclusion that expecting a group of infantrymen to spend more than a few months at a stretch in the front lines is counterproductive. Shell-shock, or battle fatigue, or whatever you want to call it, is much likelier to set in when a man has been in constant fear of his life for a really lengthy period, always wondering if the next bomb or artillery shell to come down out of the sky will have his name on it. However: if an infantry division gets pulled back from the front and has some months of relative peace and quiet, while assimilating new members who are replacing the troops who got killed or gravely wounded), then the time will come when you can send that same division back up front for a few more months with a reasonable expectation that the nerves of the seasoned veterans will generally stand up to that stress all over again . . . for awhile.
Presumably this need to take regular breaks away from the "front lines" should apply to superheroes as well. It often turns out they aren't permanently "burned out," but they definitely need the same opportunities that combat veterans often need to let their nerves settle down while they do something else for awhile.
When it comes to deliberately stepping away from the daily slugfests to recover his equilibrium, Black Lightning has been there and done that; I think multiple times. I can't find my copy right now, but I believe the following happened in "Batman and the Outsiders #5," published in 1983 as part of a team-up with the New Teen Titans of that era. At one point when the two groups were socializing, Jefferson Pierce (Black Lightning) was seen confirming to Wally West (still Kid Flash at the time) that he'd dropped out of the hero game for awhile before joining the Outsiders. Wally asked why; Jefferson said briefly that he'd made a mistake and a civilian got killed. Wally gasped out (approximately): "How can you live with that?" and Jefferson said (I think): "I couldn't -- for awhile. Batman convinced me I could still do some good, though." (All that was paraphrased from memory after I couldn't quickly find my copy, but I believe it captures the gist of their conversation.)
On a similar note, Scott Summers (Cyclops) took a long leave of absence from the X-Men after the Dark Phoenix Saga and the funeral of his beloved, Jean Grey. Certainly a plausible excuse to feel the burning need to get away from all that stressful life-and-death-decisions-in-the-heat-of-battle stuff for awhile. Scott only started working with the X-Men again about a year later (our time) in "Uncanny X-Men #150" when -- by sheer bad luck! -- he got shipwrecked on a newly-created little island and found himself a prisoner of Magneto, although he certainly hadn't been looking for Magneto and Magneto (as far as I could tell) had not deliberately come looking for Cyclops either! But when Magneto started giving ultimatums to the rest of the world, and the X-Men came flying down to fight him, Scott naturally had to help as best he could! (It must have been a nice vacation while it lasted, though. Except for the previous nerve-wracking encounter with the demon D'Spayre in the Florida Everglades, I mean, but by superhero standards, that doesn't make his vacation anything "abnormal," right?)
And in the early issues of the "Green Lantern" title that began in 1990 (with scripts by Gerard Jones), Hal Jordan was dealing with a similar feeling of "burnout." He ended up spending a few issues proving to himself that he could actually make an honest living by manual labor, deal with regular people on an equal basis, etc., without wearing the spiffy costume most of the time and without expecting his power ring to solve problems a hundred times a day for him. (But he only started doing all that after throwing himself off a cliff and only bothering to fire up his ring with his willpower -- and fly away -- in the last split-second before he otherwise would have gone SPLAT! Clearly that guy had issues and a nice long vacation was seriously overdue!)
"Nobody trusts me any more. Possibly because I made a huge fool of myself. It's time to hang up the costume and fade away!"
If people lose their faith in a superhero, there's not much point in his trying to keep fighting the good fight, no matter how great his physical condition still is. In the Astro City story arc "Steel Angel," we learned in a flashback sequence of the sad story of El Hombre, a hero in the Honor Guard of a few decades ago, who had become excessively worried about his slipping popularity. He tried to revitalize his public image by arranging for a big bad robot to go on a rampage and then he'd single-handedly do something brave and clever and deactivate it. As near as I can recall: One flaw in this "cunning plan" (besides the ethical issues involved) was that he trusted the supervillain he was dealing with to make sure the robot would be programmed to take a dive at the right moment. Surprise, surprise: It wasn't. Things got rather messy. Other heroes finally dealt with it, and tracked down the mad scientist who'd built the thing, and naturally he sang like a canary. That was the end of El Hombre as a respected figure.
(This may have been inspired by something similar that happened to Hank Pym (then known as Yellowjacket) in stories scripted by Jim Shooter back in the early 1980s, except that Hank had built the rampaging robot himself -- and still couldn't manage to deactivate it properly!)
Of course, sometimes a hero just fakes a death or retirement as a way of "resolving" the problem of Loss of Public Trust, and then finds a way to carry on, much the same as before, in one costume or another. In the late 80s, at the end of the "Armor Wars" story arc, Tony Stark made it appear that the original Iron Man, who had recently "gone rogue" (i.e. shamelessly breaking laws at the drop of a hat as he tried to seize and destroy any suits of powered armor that might derive from Stark's own designs), had died in battle. Then Tony put on a new-and-improved version of the Iron Man armor and announced that he was the new guy, whom industrialist Tony Stark had just hired to replace the old guy! Since the original Iron Man's secret identity had never been a matter of public record in those days, the average citizen of the Marvel Universe had no way to tell that Tony was lying.
Of course, longtime Avengers such as Captain America and the Wasp were bound to spot remarkable similarities in personality, fighting style, etc., between the "old guy" and the "new guy" -- although it appears that, at that point in continuity, the original Iron Man (a founding member of the team) had never explicitly unmasked himself to reveal his identity to them either -- but they were far too polite to call the "new" Iron Man a liar to his face right away. Instead, they basicallypretended to take his claims at face value, playing along for awhile and waiting to see how long it would take him to finally admit the truth to his teammates!
"I'd still be fighting the good fight if I weren't trapped in a cell."
Here, the hero never decided to quit using his abilities for the greater good -- instead, his lengthy disappearance from the public eye was literally forced upon him.
This was why the Will Payton Starman character, star of a "Starman" series of the late 80s and early 90s, was no longer actively using the Starman name on Planet Earth at the time Jack Knight's "Starman" title was launched in 1994. (Although years went by before Jack actually learned anything about this and rescued Will from captivity on an alien world.)
On a similar note: There was a time when the official version of Post-Crisis Flash continuity held that Jay Garrick spent a long, long time incommunicado, not aging and not interacting with the outside world, after some villain in the 1950s managed to place all of Keystone City (including Jay and his wife) in an otherdimensional limbo that apparently amounted to having everything and everybody in that city be in suspended animation until further notice. The villain also managed to somehow fix it up so that nobody left on the Earth of the Post-Crisis DCU had any idea that there had ever been a "Keystone City." This meant that the superheroic alias of "The Flash" had been unused for decades by the time Barry Allen dusted it off and claimed it for his own. So it wasn't that Jay had "chosen" to retire; it was just that he was not physically able to continue making public appearances. However, this has apparently become a very controversial subject among diehard Flash fans.
From what I've heard, the general understanding of what happened to Jay and all of Keystone City (in the era before the Silver Age Flash came along) appears to have gone through three stages:
1. Grant Morrison wrote "Secret Origins #50" with the intention that Keystone City was only missing for a matter of months before Barry Allen, who had very recently become the Silver Age Flash at that point, somehow rescued the city and restored it to its proper place.
2. Mark Waid later wrote follow-up stories in Wally's "Flash" title in which it was "revealed" that Keystone City had been gone for decades, from the 1950s until "several years ago," so that the inhabitants of that city had skipped a few decades of American history and suffered from massive culture shock as they tried to get caught up with the modern world. Interestingly enough: During Keystone City's very long absence, nobody else in the DCU remembered that the city or the people had ever been there! (Warning: The more you think about the ramifications of that concept, the less sense it makes!)
3. And for a long time now -- as near as I can tell from other people's comments, when I'm not a regular reader of the Post-Crisis "Flash" title or the newest "Flash" title that's replaced it -- nobody at DC has mentioned this mess at all in new stories for a good many years now, so maybe it's been "quietly retconned out" when nobody was looking and just swept under the rug as a bad idea? Or not? (DC and Marvel are both very good at totally ignoring the logical implications of their previously published stories if those implications would severely interfere with the whims of the latest writers and editors to work on a venerable concept. After all, what's more important? Being absolutely self-consistent within your shared fictional universe? Or trashing "continuity" in favor of telling any sensational story you happen to feel like telling this week?)
Accordingly: depending upon which version you choose to believe, today in the "modern DCU" Jay Garrick may or may not be a few decades younger than we would normally expect of someone who was already a grown man in the 1940s! And he may or may not have been completely "out of sight and out of mind" for decades by the time Barry Allen gained superspeed and dubbed himself "The Flash" since nobody else was using that catchy name. Don't you just love the ambiguity? :)
"I can't be seen wearing this costume in public -- we've been banned from that!"
In the world of Alan Moore's "Watchmen," largely set in an alternate timeline's version of 1985 (but with lots of flashbacks to previous events in that same timeline), an act of Congress in 1977 had outlawed amateur (civilian) costumed superheroics in the USA. The only legal way to continue a costumed career was for the "hero" to make a deal to join the government payroll. Doctor Manhattan and the Comedian had ended up working for federal agencies, and Rorschach had just ignored the law and kept working as a vigilante, but a few other heroes had simply complied with the law and faded from public view -- those heroes who hadn't died or retired prior to that date, anyway.
In the alternate timeline of Frank Miller's "Batman: The Dark Knight Returns," we eventually learned that similar political considerations had been a factor in Bruce Wayne's retirement from the Batman role -- and likewise the retirements of various other costumed heroes -- roughly ten years prior to the opening scenes of the story, except for Superman, who began working "secretly" for the federal government of the United States. Although I'm not sure if Congress had passed anything similar to the Keene Act, or if it was just a sort of informal agreement that persuaded Congress not to go to such lengths if the superheroes would just fade away quietly without any further ruckus!
Of course, in Bruce's case, he also is seen thinking about how he "swore an oath" (implied meaning: an oath to permanently quit the costumed crimefighting business) after what happened to Jason Todd, so it may be that the U.S. Congress started pressuring superheroes to either sign up or drop out at about the same time that Batman was coincidentally ready to call it quits anyway after a personal tragedy! (Otherwise they might not have found it so easy to get him to abandon his crusade no matter what laws they passed or threatened to pass!) We never got a really comprehensive explanation of the sequence of events that finally made him choose to retire "ten years ago"; just a few hints that we can try to shove together like a jigsaw puzzle.
09. Cashing In
"I worked long and hard, and now I deserve to find ways to enjoy the fruits of my labors!"
Sometimes the hero ends up abandoning full-time heroics in favor of finding other, less painful ways to pass the time and make a nice pile of money in the process.
I believe the current version of the continuity of Jonathan Law, the original Tarantula of the Golden Age, says that he was a costumed hero back around the World War II years, while also making a nice living for himself as a mystery writer. After the war, he largely abandoned the role of the Tarantula, but eventually wrote a book talking about his own adventures -- and those of other heroes he'd served with in the All-Star Squadron -- and I believe this book became a bestseller and made a nice piece of change for him.
On a similar note: In the timeline of Alan Moore's "Watchmen," Adrian Veidt, the hero once known as Ozymandias, was said to be the most brilliant mind on Earth. A couple of years before the Keene Act that I mentioned above, he had voluntarily quit the costumed hero thing in favor of using his unique genius to build a huge commercial empire that would let him pursue a larger agenda than just beating up malefactors one at a time.
10. Quitting Your Job (or Being Fired)
"Hand in your costume, clean out your desk, and scram. We don't need you around here any more!"
Some superhero roles basically are the "property" of a larger organization, rather than just being something the hero himself invented from scratch. This employer provides the costume, the alias, the public relations, sometimes a salary and expense account, and quite possibly the superpowers themselves (and/or special equipment that gives you "superhuman" capabilities when you're wearing it). The Nova Corps of Xandar bestowed powers upon you directly but reserved the right to take them back; the Green Lantern Corps issues power rings that can channel the user's willpower into all sorts of nifty effects; other employers have been known to provide cutting-edge, very expensive armored suits to their most trusted employees.
In such circumstances: If you either choose to quit or involuntarily get thrown out on your ear, then you may automatically lose the powers or special equipment that made you the mighty hero that you presumably were. This was definitely supposed to be the case -- according to the original version of events -- where the Nova Corps of Xandar was concerned. Richard Rider finally surrendered his powers in exchange for a spaceship ride back to Earth so that he wouldn't be expected to spend the rest of his life fighting somebody else's wars, far from his loved ones. That was the theory, anyway -- I was never wildly happy about the way Fabian Nicieza shamelessly retconned this "sacrifice" on Richard's part by having "New Warriors #1" start out with Night Thrasher dropping the lad who was formerly the Man Called Nova off a high roof in order to see if this extreme stress would cause his supposedly long-gone powers to reactivate within his body and let him fly to safety. After this test succeeded, Richard flew back up to where Night Thrasher was and asked how he'd known that Richard still had the powers hidden inside after all this time. Night Thrasher said, with remarkable candor, "I didn't." And yet Richard soon agreed to start working with Night Thrasher's proposed team of New Warriors!
(Would I agree to join a team that was led by a nutcase who freely admitted he had dropped me off a building just to test a wild theory that I might survive the experience unharmed if I still had superpowers secretly lurking inside me? No, I would not! I think that psychological point may actually have bothered me a lot more than the mere retcon per se that undid the "dramatic choice" Richard Rider had been forced to make years earlier when he supposedly relinquished the powers of Nova-Prime.)
Of course, some heroes who quit or are fired only feel the need to abandon one specific heroic "identity," but manage to keep fighting the good fight under a new name. Steve Rogers has done that at least twice when he wasn't being "Captain America" for one reason or another, but still wanted to help his fellow man with his special skills and all that. So he'd simply invent a new name and costume for awhile, and then carry on almost the same as before!
11. Missing in Action
"He used to be somebody -- then one day he just wasn't there anymore. I wonder what happened to him?"
Sometimes the general public (and even the other costumed heroes) of a fictional universe don't seem to know what happened to a veteran superhero many years ago; they just know that he hasn't been seen or heard from in a long, long time!
Many people are likely to assume he's dead (and this is a particularly reasonable assumption if the hero was last seen inside a building or airplane that exploded a minute later). But he may be dead or he may have experienced one or more of the other items on this list, without bothering to issue any press releases to keep the public well-informed on the nitpicking details.
In Frank Miller's "Batman: The Dark Knight Returns," we quickly learned that Batman had been in this vague, mysterious "Missing in Action" category for a solid decade from the public's point of view. We readers knew from the very start that "Bruce Wayne" was still going strong as a zillionaire sportsman, but the point is that the people of Gotham never got any sort of "Official Retirement Statement" from Batman; they only knew it had been a solid ten years since the last time he was seen running around the dark streets doing anything at all! Maybe he was dead! Maybe he was too old and feeble to exert himself that way any more! Who could say?
On the other hand: Sometimes neither the reader nor the "general public" is quite sure what happened to a guy who "used to be somebody" -- at least not in the early scenes of a story or story arc that ends up addressing that subject somehow. At the beginning of Alan Moore's classic "Whatever Happened to the Man of Tomorrow?", this is the basic situation that is quickly established re: the Silver Age Superman, who is known to have lost his powers and then vanished from public view up in the Arctic, way back when. I believe he is commonly assumed to have died up there in the ice and snow, although nobody ever retrieved the body, so there's room for argument. (The reader, of course, ends up learning exactly what happened to him, but I won't spell it out for you here.)
12. New Paint Job
"I'm still a superhero! I just switched names and costumes, okay?"
Sometimes the hero is perfectly willing to keep fighting any villains who come along, but -- for one reason or another -- he feels he must leave his old identity behind and start a new one.
I already mentioned that this can happen when a hero "quit" or was "fired" from the employment that gave him his previous identity -- but wants to somehow "stay in the game" on his own hook.
Sometimes everybody and his brother knows that a New Paint Job is exactly what happened. Around early 1984 Dick Grayson quit being Robin and became Nightwing -- new name, new costume. Near as I can tell, he made no special effort to hide the fact that "Nightwing" was the exact same guy as the "first Robin" who had been a founding member of the Titans several years earlier and had usually been their leader until very recently. On a similar note: Not long after that, another of the founding Titans, Wally West, abandoned the role of Kid Flash for good and put on a copy of Barry Allen's classic costume as he introduced himself to the world as the new Flash. I believe he actually went public with his true identity around that same time, so again, nobody was scratching his head over the "puzzle" of whatever happened to that Kid Flash character.
(And long before either of them fiddled around with new aliases, the Pre-Crisis Clark Kent had "upgraded" himself from "Superboy" to "Superman" around the time he started college, without trying to make a big mystery out of it. Everybody knew he was the same hero all along, just getting older!)
On the other hand: Sometimes a costumed hero abandons one role in order to become the "secret successor" to someone else in a better-known role, without letting the public know there has been any change.
Examples: In retcons established decades after the fact, we learned that after Steve Rogers (Captain America) was declared "Missing in Action, Presumed Dead" in April 1945, he was quietly replaced on the U.S. Army payroll by William Naslund (aka the Spirit of '76) in order to keep the role alive for morale purposes. After that gentleman died in action, the next Captain America was Jeff Mace, who had previously used a costumed role called The Patriot during the WWII era. As far I can tell, any ordinary American citizen in the Marvel Universe of the 1940s and 1950s who'd been a special fan of the Spirit of '76, for instance, probably never knew what really happened to that hero. Those heroes appeared to have just vanished off the face of the earth, but modern readers know that they simply sacrificed their old costumed identities in order to perpetuate a much bigger one as a patriotic duty!
(In the late 80s, it happened again when John Walker, the second Super-Patriot, was recruited to be yet another Captain America -- without the fact of a recent change behind the mask being made public immediately.)
13. Turning to the Dark Side of the Force
In #6, "Disgraced," I mentioned a few cases where a hero damaged his own public image enough that he had to drop out of the superhero business. However, the cases I was thinking of (and mentioned) were ones where the hero clearly wanted to keep doing the superhero bit, despite the occasional lapse of judgment.
But some heroes choose (or so it seems at the time) to "go bad" of their own free will, as opposed to just getting into the occasional "scandal" and immediately regretting one or two hasty misjudgments. We've had Hal Jordan quit being Green Lantern and call himself Parallax (thereby making room for Kyle Rayner to take over the Green Lantern title), we've had Jean Grey go nuts as Dark Phoenix (and then die, leaving room for Rachel Summers to later pop up as the new "Phoenix"), we've had Colossus defect to Magneto's side of the fence (but keeping the use of the name Colossus at the time), and sometimes we've learned that a putative hero was always rotten to the core but did a good job of hiding that for awhile from other heroes. Tara Markov (Terra I) serves as a prime example of that approach. Although the reader got warned several months earlier, her fellow Titans did not realize what she really was until after she had already betrayed their secrets to her ally, Deathstroke the Terminator, in "The Judas Contract." Then she died in battle -- basically killed herself in a fit of berserker rage -- before the Titans could find any good way to deal with the problem.
And, of course, last year Cassandra Cain, formerly the third Batgirl, became leader of the League of Assassins . . .
(Of course, many such heroes get dragged through the mud and then later get "Rehabilitated" via such excuses as "I was secretly being Mind-Controlled" or "That wasn't me; it was an Impostor!" But that's a different problem; one I've written about before, as you'll see on the list below!)
P.S. Whenever I do something this ambitious, I take it for granted there's still room for improvement. If you think I completely skipped a possible reason for a superhero to get out of the game, or if you see some errors in the stuff I actually typed about one previously published story or another, then please speak up! One of these days I may actually incorporate your constructive criticism into a revised draft of this list!
Meanwhile, if you actually enjoyed reading this and want to see what other "Numbered Lists" I've done over the last three years to sort out my own ideas about some of the peculiarities of superhero comic books, then you might try some of these links: