As anyone who has followed comics for long enough knows, one of the most important aspects of  a superhero is the villains. Mark Gruenwald once said that every solo superhero should have at least 12 good supervillains, so that they could theoretically have a different good villain each month without repetition. Obviously, not a whole lot of superheroes can actually meet those high standards, but one of the go-to ideas that comic book writers have used over the years was to create evil versions of the main superhero.

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Here, we will count down the greatest instances of evil version of superheroes in comic book history. Note: we're talking about characters who were specifically created to be opposites of established characters, not retroactive stuff like Chris Claremont having Sabreooth and Wolverine meet a decade into Sabretooth's comic book career. In addition, we're not counting Bizarro as an "evil version" of Superman, since Bizarro isn't really evil. Otherwise, enjoy!

15 IRON MONGER

iron-monger

Almost as soon as Iron Man began appearing in his own feature in "Tales of Suspense," Marvel introduced other armored villains to fight him. When you have an armored hero, that's just plain logical. Especially in the early days of Marvel when the bad guys were typically Communist, it was easy to have a Soviet villain in a suit of armor. Both the Crimson Dynamo and the Titanium Man served Iron Man well as recurring villains. Similarly, since Tony Stark was a business leader, it made sense to introduce evil businessmen as well, like Justin Hammer, who supplied supervillains with powers for a cut of their takings.

However, with Obadiah Stane, Denny O'Neill managed to combine both ideas into one. When Tony Stark was dealing with a relapse into alcoholism, rival industrialist Obadiah Stane bought Stark International right out from beneath Stark's feet. When Stark finally got sober and introduced a brand-new Iron Man suit, Stane also developed his own armor, calling himself the Iron Monger. Despite being out-muscled, Iron Man's experience won the day and Iron Monger responded by killing himself.

14 FRIGHTFUL FOUR

In the early days of the Fantastic Four, while Stan Lee and Jack Kirby created an amazing villain with Doctor Doom, otherwise the Fantastic Four had slim pickings in terms of recurring villains. The Red Ghost fought them a couple of times, but for the most part, it was Doom or bust. That changed with the introduction of the Frightful Four in "Fantastic Four" #36. The team consisted of the Wizard (the Mister Fantastic equivalent), Medusa (the Invisible Girl equivalent), Sandman and Paste Pot Pete (debatable as to who each of those guys were supposed to be the counterparts to, Human Torch or Thing). The Sandman was a particularly interesting addition to the team, because up until that point he had been a Spider-Man villain.

You could tell that Lee and Kirby liked the Frightful Four because they used them an amazing amount of times in a very short period. However, once they decided to make Medusa a member of the Inhumans and a hero, the team has never quite been the same since. For a while, though, they (together) were the Fantastic Four's #2 villain.

13 IKARI

Even before he began to work with artist Chris Samnee on a long and incredible run on "Daredevil" together, writer Mark Waid had been putting in hints about a mystery villain who was trying to ruin Daredevil's life. One of the ways that this mysterious bad guy figured out how to mess with Daredevil was to test out the same radioactive chemicals that gave Daredevil his powers on homeless guys. Finally, the mysterious mastermind (who turned out to be a paralyzed Bullseye, having only his brain to fight with -- which turned out to be just as deadly as every other part of his body) unleashed Ikari on Daredevil.

Decked out in a variation of Daredevil's original costume, Ikari handled Daredevil well, causing The Man Without Fear to try a gambit he thought would work based on Ikari being new to his powers. However, Ikari then shocked Daredevil by revealing that he could see! The experiment had given him Daredevil's radar sense but had not taken away his eyesight! It was a total game-changer.

12 DARK BEAST

During the "Age of Apocalypse" storyline, the entire reality of the X-Men was shattered, as Legion had gone back in time and accidentally killed Charles Xavier when he was a young man. The battle that led to Xavier's death woke Apocalypse up years early, before the age of superheroes, so Apocalypse was able to conquer Earth easily, while Magneto had to form the X-Men in honor of his dead friend.

While many of the X-Men remained heroes in this new reality, some of them became villains. One of the main new villains was Beast, who became Mister Sinister's chief scientist in this new reality, performing terrible experiments on mutants with glee. When the "Age of Apocalypse" reality was destroyed, four characters managed to cross over to the main Marvel universe. One of them was Dark Beast. Dark Beast was great because he took Beast's trademark humor but applied it to evil. It was so twisted that it was a lot of fun to read.

11 ABOMINATION

abomination

In the late 1960s, Marvel received a major coup when they managed to convince Gil Kane to leave DC Comics and come to work for Marvel. Kane ultimately settled into a stint where he was Marvel's main cover artist in the 1970s, as well as working on some major projects like "Amazing Spider-Man" after John Romita left the book. However, the first assignment he had was the "Hulk" feature in "Tales to Astonish."

Stan Lee basically said to Kane, "Let's come up with a character who would be stronger than the Hulk!" Their creation turned out to be the Abomination, a Soviet spy who was exposed to gamma radiation and became an even more powerful version of the Hulk. They ultimately realized that he was too strong, and he was soon powered down, but the Abomination became one of the Hulk's top recurring foes. It was rare to see a villain who could go toe-to-toe with the Hulk!

10 LEGION OF SUPER-VILLAINS

One of the big hooks with the Legion of Super-Heroes was that the superpowers of their members were typically abilities that everyone on their given planet had. Therefore, that opened up the idea that for every good hero from those planets, there might very well be an evil version, as well! Amazingly enough, the Legion of Super-Villains appeared almost right after the heroic Legion debuted, only they showed up as adults who captured Superman as an adult rather than the Superboy who was a member of the Legion of Super-Heroes.

Later on, the Legion of Super-Villains, who were contemporaries with "our" Legion, showed up and became major thorns in the sides of the heroic Legion, especially in the launch of the Legion's "Baxter" series in 1984. DC had taken their two most popular titles, "New Teen Titans" and "Legion of Super-Heroes" and launched them in special "Direct Market" editions on fancier paper (called "Baxter" paper), as well as fancier coloring and other production values. The Legion of Super-Villains were the main bad guys in the launch of this new series (by Paul Levitz, Keith Giffen and Larry Mahlstedt) and they ended up killing off Karate Kid!

9 SUPERBOY PRIME

Superboy-Prime

This one is a bit tricky, as while Superboy Prime clearly was intended to be an opposite of Superboy right from the start, he was intended to be a good opposite at first. Well, not even necessarily good, but certainly not evil. Superboy Prime was introduced in the lead-up to "Crisis on Infinite Earths," as the Superboy from the "real world" (Earth Prime). When "Crisis on Infinite Earths" ended with a rebooted Earth, a handful of survivors from other Earths (Superboy Prime, Alexander Luthor from Earth 3 and Superman and Lois Lane from Earth 2) went to another place altogether.

During their time away, they watched as they saw the heroes of the DC Universe "waste" the opportunity given to them during "Crisis." Ultimately, Luthor and Superboy became obsessed with fixing the mistakes of the DC Universe and Superboy Prime just snapped, deciding it was okay to kill these heroes, since they had ruined things. Superboy Prime then became a powerful recurring villain, always intent on "fixing" things to the way that he wanted them to be.

8 DARK AVENGERS

After "Civil War," Tony Stark was given unparalleled control, including becoming the new head oF S.H.I.E.L.D. However, soon afterwards, the Skrulls took advantage in some weaknesses in Stark's technology to invade Earth under Tony's nose. This might have been an unfair criticism (as they likely would have beaten any security), but whatever the criteria, Tony Stark got the blame and Norman Osborn, who had been running the United States government's team of villains, the Thunderbolts, became the big hero (because he delivered the final kill shot on the Skrull's queen).

Osborn then turned S.H.I.E.L.D. into H.A.M.M.E.R. and created his own Avengers team consisting of evil versions of superheroes, with Bullseye becoming Hawkeye, Moonstone becoming Ms. Marvel, Venom becoming Spider-Man and Logan's disturbed son, Daken, becoming Wolverine. After Osborn was deposed as head of H.A.M.M.E.R., he then put together another team of Dark Avengers (with Trickshot being the new Hawkeye and Superia the new Ms. Marvel).

7 CYBORG SUPERMAN

After the historic "Death of Superman," DC shocked the world with its follow-up storyline, "The Reign of the Supermen," where four new people showed up claiming to be Superman (well, three of them claimed to be Superman, at least, Steel only said he was inspired by Superman). One of the these Superman was a cyborg who claimed that he was the return of Superman, only partially made out of cybernetic parts. He certainly looked the part, at least.

As it turned out, though, the Cyborg was actually Hank Henshaw, an old Superman villain who took the opportunity of Superman's death to trick the world into believing he was a hero. The Cyborg Superman then cut a deal with Mongul to bring Warworld to Earth. They then destroyed Coast City and tried to blame it on one of the other Supermen. After the real Superman returned, Cyborg Superman became a recurring foe, but nothing beats that initial destruction of Green Lantern's home town (which also led to Green Lantern snapping and becoming evil himself).

6 CRIME SYNDICATE OF AMERICA

One of the earliest crossovers between the Justice League of America and the Justice Society of America also introduced the Crime Syndicate of America to the DC Universe. The concept of infinite Earths was still a new invention at the time, and the world of the Crime Syndicate was the third Earth that we knew about (it was also officially Earth-3). The world was ruled by evil versions of the Justice League, including Ultraman (Superman), Superwoman (Wonder Woman), Owlman (Batman), Power Ring (Green Lantern) and Johnny Quick (Flash). After their initial appearance, they did not pop up all that often before seemingly being killed during "Crisis on Infinite Earths."

During his run on "JLA," though, Grant Morrison introduced a new version of the Crime Syndicate in the classic graphic novel, "JLA: Earth 2," with art by Frank Quitely. This Crime Syndicate is a lot darker than the previous version, and Morrison introduced a novel twist that the Crime Syndicate could not win on this Earth and our Justice League can never win on their Earth. The Crime Syndicate were also the main villains in the New 52 crossover event, "Forever Evil."

5 BLACK ADAM

Amazingly enough, Black Adam debuted in "The Marvel Family" #1, kicked a lot of butt all issue long and then died at the end of the issue. He then did not appear in another comic book for 30 years! But when he was rejuvenated in the 1970s, after DC Comics licensed the rights to the Marvel Family characters, he quickly became one of Captain Marvel's key nemeses.

When Captain Marvel was rebooted by DC Comics in the 1990s, Black Adam suddenly played a central role in his creation. Adam was given his powers by Shazam in ancient Egypt by reciting the name "Shazam," which for him stood for the stamina of Shu, the swiftness of Heru, the strength of Amon, the wisdom of Zehuti, the power of Aton and the courage of Mehen, but then Adam was corrupted and became evil. In modern times, Black Adam was almost an anti-hero, as he felt that his actions were just, even if they involved killing lots of people. Black Adam is set to get a major motion picture before Captain Marvel, which shows how interesting he can be!

4 MAGUS

magus raising his gauntlet

When Jim Starlin took over the "Warlock" feature in "Strange Adventures," there were so little expectations that he basically could do whatever he wanted with the character and he soon began an epic so interesting that Marvel brought back Warlock's previously canceled comic book series and let Starlin start it back up. The main villain of Starlin's epic was a mysterious being known as the Magus, who created the evil Universal Church of Truth. Warlock soon discovered the truth about Magus --- he was Warlock from the future!! Eventually, Warlock had to sacrifice himself to stop himself from ever becoming the Magus.

Later on, at the end of the "Infinity Gauntlet" crossover (when Warlock had been resurrected), Warlock temporarily had the Infinity Gauntlet. While it was in his hands, he split off both the good and the evil side of himself. The evil side became a new Magus, who caused the battle that led to the "Infinity War." He has popped up a few times since, as time doubles are always hard to pin down.

3 REVERSE FLASH

The Reverse Flash is one of those characters where he was a big deal when he debuted, but he only got bigger and bigger in the Flash's history as the years went by. Eobard Thawne was living in the future when he discovered a time capsule containing the Flash's costume. He was able to use the residual speed on the costume to give himself super speed. He took the name "Professor Zoom" and traveled to the past to fight against his inspiration. He fought against the Flash a number of times before he took things to a whole other level when he murdered the Flash's wife, Iris Allen. When Barry eventually remarried, Zoom tried to kill her, too, but the Flash instead killed him before he could kill her.

After the "Crisis on Infinite Earths," the Reverse Flash returned and killed Barry Allen's mother when Barry was just a boy. This also framed Barry's dad for the crime. When Barry tried to reverse his actions, it changed his entire timeline for the worse ("Flashpoint" was what the new universe was called), so Barry had to let his own mother die. The Reverse Flash is set to re-appear in a major Batman/Flash crossover coming up soon.

2 SINESTRO

When we think of Hal Jordan as the greatest Green Lantern of them all, it is important to note that at one point, the answer to the question, "Who is the greatest Green Lantern of them all?" was Sinestro. He was the pride of the Green Lantern Corps, but eventually grew so obsessed with order that he became a tyrant. One of the great retcons of the DC Universe is the revelation that Sinestro was Hal Jordan's training officer when Hal became a member of the Green Lantern Corps. That adds a whole new level of awesomeness to their relationship.

For years, Sinestro had a yellow power ring that created yellow constructs, which Green Lantern rings could not stop. Eventually, he created his own Sinestro Corps, filled with people who know how to instill great fear instead of being able to overcome great fear, like the Green Lanterns. Sinestro is a fascinating villain and even briefly had his own ongoing series.

1 VENOM

Spider-Man is an intriguing superhero in the sense that his greatest enemy has changed a number of times over the years. If you asked who Spider-Man's greatest foe was in, say, 1967, you would get a different answer than 1977 or 1987 or 1997. Amazingly enough, one of his greatest foes did not even appear until Spider-Man had been around for 25 years. In "Amazing Spider-Man" #300 (after a brief intro at the end of the previous issue), we met Venom, who was a tarnished reporter, Eddie Brock, merged with an alien symbiote that Spider-Man had rejected a few years earlier.

Venom now looked like a monstrous version of Spider-Man (in his black costume) and since he had once bonded with Spider-Man, the symbiote canceled out Spider-Man's Spider-Sense, making him a much deadlier foe. He tormented Spider-Man for years until they formed a brief truce. Even when that happend, the Venom symbiote yielded dangers, creating another symbiote that bonded with a serial killer to form Carnage, who was enemies with Spider-Man and Venom. More recently, Venom had been used for a force of good, but through no fault of the alien costume itself (but rather his new bloodthirsty host), he has returned to a life of evil.

Who is your favorite evil version of a superhero? Let us know in the comments section!