Considered by many to be the greatest comic book villain of all time, it’s tough to imagine a more perfect foil for Batman than the Joker. After being thwarted by Batman on so many occasions however, it’s Joker’s sheer unpredictability and penchant for the sadistic that has kept him a consistently imposing figure over the decades. There are very few things the Joker won’t do to make a point, and as a result has been front and center for the vast majority of Batman’s (as well as the DC Universe’s) darkest hours.

With that said, there’s a surprising amount of times that Joker has fought on the side of good for one reason or another. While most of the Joker’s good deeds were done in the interest of keeping Batman alive -- and therefore preserving the twisted game between them -- there are also rare instances where the Joker appears to have shown a brief glimmer of humanity. Sure, his evil deeds far outweigh his altruistic ones, but it’s always interesting to explore what the Joker is and isn’t willing to do in his ideological war with Batman. With that in mind, here are the 10 sickest acts committed by the Joker, as well as the 10 most heroic.

20 BAD: TAKES ROBIN ON A CHRISTMAS EVE CRIME SPREE

It’s no surprise that most of the Joker’s most depraved acts tend to stem from larger, more important Batman stories, ones that explore the twisted relationship between the pair. Occasionally though, a single standalone issue can leave just as much of an impression on its readers than their larger-scale counterparts.

Take 2007’s Detective Comics #826 for instance, which sees the Joker kidnap Robin, and on Christmas Eve no less. Tying him up with rope and Christmas lights, Joker circles the streets of Gotham in his car, forcing the Boy Wonder to watch as he casually mows down innocent bystanders. He even makes a stop at a local fast food restaurant, cruelly executing the manager when a worker fails to take his order. While Robin eventually frees himself and puts a stop to Joker, the damage is unfortunately already done, leaving Robin distraught over his inability to help.

19 HEROIC: HELPS BATMAN CURE A DEADLY VIRUS

The idea that Batman and the Joker are two sides of the same coin is long-rooted in the Batman mythos, and it’s because the two characters play so well off each other. It’s often suggested that the duo have an unhealthy dependence on each other, making their complicated relationship all the more messed up and Batman: Europa takes this idea and makes it literal.

Infected with a lethal virus that threatens to drive him insane before killing him, Batman is forced to team-up with a similarly infected Joker to find a cure. Embarking on the world’s weirdest road trip across Europe, the pair form an odd kind of bond as their symptoms worsen, gaining a deeper insight into each other’s psyches. Naturally, the two men are soon back at each other’s throats once they find the cure -- and we wouldn’t have it any other way.

18 BAD: EMPTIES A LIVE STUDIO AUDIENCE

One of several disturbing moments from Frank Miller’s seminal classic The Dark Knight Returns, an aged Joker’s appearance on David Letterman stands as one of the story’s most memorable moments.

Appearing on the show as an example of a “victim of Batman’s psychosis”, it’s immediately clear that things are about to go awry when the show’s guests fail to take the Joker seriously. Abruptly announcing mid-interview that he’s going to kill everyone in the room, his outburst is foolishly brushed off as a joke at first -- before the room quickly begins to fill with gas. Dosed with the Joker’s infamous toxin, the audience dies in uproarious laughter, with Joker taunting his fellow guests as they die in agony.

17 HEROIC: TRIES TO SAVE GOTHAM

Although the ongoing war between Batman and the Joker has always been an integral part of the Caped Crusader’s decades-long saga, it’s surprising to see that it took so long for someone to flip the script, so to speak -- envisioning a world where Joker was the one trying to save Gotham, while Batman was the one tearing it apart.

In Sean Murphy’s Batman: White Knight, we’re introduced to a fully reformed Joker, now Jack Napier, who becomes a prominent political figure after delivering a series of impassioned speeches about Gotham’s corrupt 1%. After Batman takes his crusade for justice too far however, Napier decides that it’s in fact Batman who may be responsible for the city’s dire situation. Depicting a Joker who genuinely cares about saving Gotham and its citizens, this is probably the most heroic the character has ever been, even if it is out of continuity.

16 BAD: DRIVES TIM DRAKE INSANE

While several of Batman’s animated outings are well known for their often-grim subject matter, one of the Caped Crusader’s darkest on-screen moments comes in the animated movie Batman Beyond: Return of the Joker. After capturing Tim Drake, the current Robin and Bruce Wayne’s protégé, the Joker proceeds to torture the Boy Wonder for three full weeks, with Batman eventually managing to track him down.

Coming face-to-face with a psychologically damaged Robin (complete with fully-fitted Joker attire), the Clown Prince of Crime urges his new pet to shoot Batman as Tim laughs uncontrollably. Able to overcome his madness for long enough to shoot the Joker dead instead, Robin’s maniacal laughter soon turns to hysterical tears, leaving him a completely broken man. The way the whole scene is shot is just incredibly chilling -- and is frankly anything but child friendly.

15 HEROIC: STOPS BATMAN FROM ENDING THE RIDDLER

One of the best Batman stories in a long time, “The War of Jokes and Riddles” follows the Caped Crusader as he gets caught in the middle of an ever-escalating war between two of Gotham’s most deranged criminals in the Joker and the Riddler.

After going through hell to try and quell the violence between the two factions, it’s eventually revealed to Batman that Riddler had orchestrated the entire conflict in a futile attempt to make the Joker laugh. Infuriated by the revelation, something inside Batman snaps. In a legitimate attempt to kill the Riddler, Batman thrusts a knife towards his face, only for the Joker to intercept the blow with his hand -- keeping Batman from breaking his one rule. While the Joker’s motivations aren’t entirely clear here, perhaps he wants to be the one to break the Bat, there’s no question that nothing but good ultimately came from his actions.

14 BAD: CREATES HARLEY QUINN

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There could be a whole list in itself of terrible things the Joker has done to Harley Quinn, his cruel manipulation and abuse of her further outlining the villain’s lack of humanity towards even those closest to him. There’s no question that the worst thing the Joker ever did to Harley Quinn however, was create her.

Debuting in Batman: The Animated Series, Harleen Quinzel was the Joker’s psychiatrist, who began to sympathize with what the man she deemed a “tortured soul”. Eventually succumbing to the Joker’s sinister influence -- after extensive physical and psychological torture, depending on which version we’re talking about –- Quinzel is reborn as Harley Quinn, the Joker’s sort-of-girlfriend, partner in crime, and plaything. Sometimes drawn towards good, Harley’s tug-of-war between staying with the abusive Joker and forging her own identity echoes real-life abusive relationships -- and makes Joker’s awful treatment of her truly hard to watch.

13 HEROIC: KEEPS BATMAN’S IDENTITY SECRET

Throughout the entirety of Batman: White Knight, we’re waiting for the newly-heroic Joker to finally uncover his true plan, revealing his villainous intentions in a third act “gotcha!” moment that would restore the status quo between Batman, the Joker and Gotham City. Smartly though, this twist never really arrives -- in this manner at least -- at any point in the story.

This version of the Joker truly is reformed, wanting the best for Gotham even if it means locking up the man who was once considered the city’s savior. He even doubles down on his good deeds once Batman is apprehended, refusing to let the GCPD unmask the vigilante after promising he’d keep his identity secret. DC’s main universe Joker has likely kept Batman’s identity secret in the past in order to perpetuate their little game, but this is the first time he’s done so in a selfless manner.

12 BAD: DOESN'T RESPECT HIS HENCHMAN

While Brian Azarello’s 2008 graphic novel Joker received critical praise for its uncompromising glimpse under the hood of Batman’s greatest enemy, it also received some blowback for making the Joker just a little bit too repulsive, if that’s even possible. Needless to say, the story contains some truly shocking Joker moments that really push the envelope of what the character is willing to do to his victims.

While his most disturbing act in the story is perhaps a little too controversial to even mention here, Joker’s most gruesome moment comes when the villain decides to take precautionary measures against his loose-lipped henchman, Monty. Following him into the back room of a club, the Joker skins his former ally alive from neck to toe, allowing him to stumble out of the room for one final moment before succumbing to his grotesque injuries.

11 HEROIC: HELPS BATMAN STOP PENGUIN

Given the polar opposite desires of Batman and the Joker, it’s incredibly rare that the goals of the two men ever actually align. Every once in a while, however, the duo gets to test the theory that they’re hopelessly dependent on one another.

The Brave and the Bold #191, for example, places the Joker and Batman on the same side when the former is framed for the murder of Oswald Cobblepot, better known as the Penguin. Realising that the Joker may in fact be innocent of the crime, the pair team up to discover the truth behind the Penguin’s demise. It turns out that Cobblepot faked his own death to facilitate the capture of a high-ranking Catholic official, and the Joker is cleared of the crime -- one of many, that is.

10 BAD: REPEATEDLY ENDS BATMAN, EATS CHINA

Much like his greatest foe Batman, the Joker is one of the most formidable characters in the DC Universe despite his complete lack of superpowers. Relying solely on his unique brand of cold, calculating (and darkly humorous) genius to torment the residents of the DCU, superpowers are dead last on the list of things the Joker should have.

That’s exactly what he gets however, when he leeches the reality warping powers of Mr. Mxyzptlk in the “Emperor Joker” storyline. Rebuilding the Universe in his own twisted image, the Joker entertains himself by repeatedly murdering Batman in brutal fashion, constantly resurrecting him to keep up the fun for as long as possible. As if that wasn’t bad enough, the Joker also uses his newfound powers to eat the entirety of China, cruelly cracking wise as he does so.

9 HEROIC: TAKES DOWN OWLMAN

Despite his penchant for creating chaos wherever possible, the Joker has also been known to lend a helping hand when the situation calls for it. This is exactly what happens in “Game Over For Owlman!”, an episode of the Batman: The Brave and the Bold that sees the unlikely pair join forces.

When an alternate universe version of Batman known as Owlman begins to wreak on Gotham City -- as well as Batman’s reputation -- the Caped Crusader is forced to turn to the only person he can count on to take out a twisted version of himself: The Joker. As you might expect, Joker is ecstatic at the thought of teaming up with Batman, especially when it involves taking down another Batman in the process. Surprisingly enough though, the duo proves to be an effective team, swiftly defeating Owlman before resuming their antagonistic relationship.

8 BAD: FORCES SUPERMAN TO DO SOMETHING HE'D NEVER DO

superman injustice

While the war between Batman and the Joker has given way to some of the darkest moments in Batman’s entire career, the Clown Prince of Crime apparently isn’t content with ruining only Batman’s life. In one of the darkest Superman stories ever, the Injustice series of comics and video games kicks off proceedings by having Joker force a Kryptonite-based variant of Scarecrow’s fear gas on Superman. Believing himself to be locked in a deadly battle with Doomsday, Superman defeats his foe -- only to later discover that “Doomsday” was in fact Lois Lane.

What’s worse is that Lois Lane also happened to be pregnant at the time. What’s even worse is that her death detonates a nuclear bomb that completely obliterates Metropolis. Understandably, the whole ordeal causes Superman to snap, taking out Joker before establishing an oppressive, totalitarian regime to ensure nothing like this ever happens again.

7 HEROIC: FEELS GENUINE REGRET FOR HIS ACTIONS

The Lazarus Pits have a notable tendency to give its users a whole host of peculiar side effects as a trade off for its uncanny ability to bring people back from the dead. Perhaps the strangest side effect of the Pits however was experienced by the Joker himself. After being killed by Talia Al Ghul, the Joker is carried to the Lazarus Pits by Batman and Alfred in 2001’s Batman: Legends of the Dark Knight #145.

After the Joker’s life is restored however, Alfred makes a startling discovery -- the Joker has become sane. Temporarily, at least. Claiming to feel “odd” and “distanced”, the Joker begins to feel immense regret for his horrific actions over the years, lamenting that being sane is “such a burden.” Unsurprisingly, it doesn’t take long for the Joker to snap out of his temporary sanity, and soon resumes his post as Batman’s most feared adversary.

6 BAD: TRICKS PEOPLE AT A CARNIVAL

Perhaps one of the most purely evil acts the Joker has ever committed, The Dark Knight Returns sees the villain set up shop at a carnival, handing out free cotton candy to an enthusiastic group of scouts that stop by. In a textbook case of why you should never take candy from a stranger -- or in this case cotton candy from a clown -- the sugary treat has actually been poisoned, presumably killing the entire group.

Hoping his vile crime will finally cause Batman to snap and kill him, the Joker also slaughters dozens of young couples in the Tunnel of Love for good measure, before the Bat catches up with him. With the Dark Knight able to overcome his urge to kill the villain, a disappointed Joker ensures he has the last laugh by snapping his own neck -- essentially framing Batman for his murder.

5 HEROIC: BECOMES A DETECTIVE, HELPS DICK GRAYSON

After Batman is shot back in time by Darkseid during the events of “Final Crisis”, Dick Grayson briefly takes up the cowl, becoming the Caped Crusader in his mentor’s absence. Dealing with an overwhelming variety of new threats at once, Grayson is relieved to receive assistance in handling the El Penitente Cartel from a mysterious figure known as Oberon Sexton -- a British true crime author and detective.

As it turns out, Oberon Sexton is in fact the Joker in an elaborate disguise. With the cartel attempting to blackmail the villain into murdering Batman, Joker decides to assist Dick in his pursuit of El Penitente instead. The Joker did murder the actual author (and murderer) known as Oberon Sexton to appropriate his identity however, so this one’s a kind of heroic act wrapped up in a villainous one.

4 BAD: THE JASON TODD SITUATION

Line up all of Batman’s most famous story arcs, and you’re almost certainly going to find “Death in the Family” amongst them. Marking arguably the lowest point in the Dark Knight’s entire career, the story was famous for putting the fate of Jason Todd -- the second, less popular Robin -- up to a vote.

The results were surprisingly close given the community’s general dislike of Todd, but the character was ultimately killed off by popular demand. Kidnapped and tortured by the Joker, Jason was brutally beaten to a pulp with a crowbar as Joker took his time dishing out the punishment. Batman eventually arrived on the scene, only for a time bomb to detonate the warehouse containing Robin before Batman could save him. The death weighed heavily on Batman for years to come and remains one of the most pivotal moments in comic book history.

3 HEROIC: JOINS A JUSTICE LEAGUE TEAM

Yeah, you heard that right. In 2001’s six-issue Justice Leagues limited series, the world was forced to forget the existence of the Justice League of America following a psychic attack by Hector Hammond. In its place, other, more obscure versions of the team began to materialize -- including the Justice League of Atlantis and the Justice League of Amazons -- but the most interesting team to come out of the event was the Justice League of Arkham.

Led by Batman and Nightwing, the team consisted of Poison Ivy, Catwoman, the Riddler, the Ventriloquist (as well as his puppet, Scarface) and of course, the Joker. Tasked with foiling Advance Man’s plans to release toxic gas into Gotham’s water supply, the team helped Batman to a certain degree, before abandoning him mid-mission to escape imprisonment.

2 BAD: HURTS BARBARA GORDON

Thirty years on, Alan Moore’s The Killing Joke remains one of the most iconic, critically praised and controversial stories ever to come out of DC. Cutting back and forth between the Joker’s tragic origin story and his present-day plans to torment Commissioner Gordon into madness, the story drew some criticism from fans for its brutal treatment of Barbara Gordon.

Showing up at Barb’s place, Joker greets her with a bullet to the gut, irreparably damaging her spinal cord and leaving her paralyzed. As if this wasn’t chilling enough, Joker proceeds to strip Barbara down before photographing her in her vulnerable, traumatized state -- all before showing the pictures to a beaten and bound Jim Gordon. There’s been much debate over what exactly transpired between the Joker and Barbara Gordon during the attack, but whichever way you look at it, it stands out as perhaps Joker’s most heinous act of all.

1 HEROIC: TAKES DOWN RED SKULL

Set in an alternate reality World War II -- in which the Dark Knight happens to share a Universe with the Star-Spangled Avenger -- John Byrne’s Batman & Captain America ups the ante by having the duo fight off the combined might of their respective arch-enemies: the Joker and Red Skull.

That said, even the Clown Prince of Crime occasionally knows where to draw the line. After realizing he’s been assisting a Nazi the entire time, Joker turns on his former partner, stating that although he’s a criminal lunatic, he’s an American criminal lunatic. He’s captured by Red Skull for his efforts, but eventually manages to break free, thwarting the villain’s plans to drop a nuclear bomb on Washington -- presumably dying in the process.