The Joker is one of Batman's most iconic adversaries, having made his villainous debut over eighty years ago in 1940. Since then, the character has evolved, significantly expanding his arsenal and assuming many different incarnations as Gotham's most sinister face of evil.
The Clown Prince is so unique that many characters of various anime bear an astonishing resemblance to him, one so prodigious that he might arguably be their inspiration. Through examining these individuals, we can better appreciate the Dark Knight's worst foe and the other antagonists that strongly resemble his unique brand of evil.
10 Nui Harime (Kill La Kill)
Despite her innocent appearance, Nui Harime was the servant of Ragyo and the murderer of Ryuko's father. She took great delight in tormenting her foes before killing them, mocking Matoi for her parent's death and the role she personally played in it.
This is strongly redolent to the Joker's own inclinations, especially through how cruelly he toyed with Batman over the alleged "death" of Jason Todd and the many other characters that the Dark Knight failed to save. The only difference between Harime and her clown counterpart is that she was willing to die out of a sense of duty toward her mistress.
9 Mad Pierrot (Cowboy Bebop)
The Mad Pierrot was a man whose body had been enhanced through the cutting edge science of the time, rendering him Spike Spiegel's most powerful adversary. However, his mind was shattered as a consequence, reducing him to the giggling and depraved freak that the bounty hunter encountered in the series.
Similarly, the Joker's mania is due to his own troubled past—specifically, his most commonly accepted backstory of falling into a vat of chemicals and losing himself because of them. Both men have been irreversibly changed because of what had been done to them, showing no signs of potential redemption.
8 Hisoka (Hunter X Hunter)
Hisoka was one of the first villains introduced to the Hunter X Hunter series. He was obsessed with his opponents' strength and the challenge they might pose before he inevitably defeats them, with the battle—and death that ensues—being his primary drive throughout the story.
Curiously, his willingness to spare Gon resembles Joker's own reluctance to permanently kill Batman. On multiple occasions, he has turned down the opportunity since it wasn't the "right time" or because the Dark Knight was "too much fun."
7 Orochimaru (Naruto)
Orochimaru was the maniacal fallen Sannin of Konoha and one of the Leaf's oldest living enemies, similar to the Joker's own relationship with Batman. Of Naruto's foes, he has the most diverse and sadistic arsenal by which to kill his victims, relishing in their suffering as he achieves his own ends.
His weaponry, and penchant for poisons, draw a disturbing number of parallels between himself and the Clown Prince. Their primary motivation is to cure their own boredom—regardless of how many lives they must end for a moment's satisfaction.
6 Cioccolata (JoJo's Bizarre Adventure)
Cioccolata was one of Diavolo's most depraved henchmen and perhaps the evilest side character in the entire series. His Stand could secrete a noxious mold that affected many victims from afar, allowing him to murder dozens of people from relative obscurity.
This is much like Joker's own laughing gas, which he has deployed against Gotham's unfortunate residents on many different occasions. On top of their physical resemblances, both villains also have a sidekick that was a former—or current—subject of their abuse through Secco and Harley Quinn.
5 Syura (Akame Ga Kill!)
Syura was the son of Minister Honest and one of the few individuals whose malice could possibly eclipse his father's. Instead of wishing to rule the empire through an onerous boot, he sought only to use his future subjects for his own amusement, basking in the agony he could inflict against them.
This is much akin to Joker's own inclinations, especially when he is given any semblance of power. An example is gleaned from the Emperor Joker arc, where he had twisted reality itself to accommodate his unhinged desires.
4 Buggy The Clown (One Piece)
Buggy the Clown's similarities with the Joker take after his more benign iterations. Though the Devil Fruit user is particularly menacing, his willingness to hurt others is usually an indirect result of his greed—whereas the Clown Prince is the opposite.
Nonetheless, it's impossible to excuse what they have in common. In addition to their physical resemblances, their subordinates also share their bizarre likeness. Moreover, they're both wanted criminals and have earned a notorious reputation for the many remorseless actions they have taken in order to fulfill their desires.
3 Barry The Chopper (Fullmetal Alchemist)
Barry the Chopper was a man whose soul had been infused into a suit of armor due to the crimes he had committed against the people of Amestris. As his name suggests, he was a mass murderer who relished mutilating his opponents' bodies.
He shares the Joker's maniacal disposition and crazed laughter amidst the heat of battle, viewing the many people he had murdered as an accomplishment rather than a point of regret. This makes him an incorrigible monster regardless of how much Alphonse Elric had attempted to reason with him—or in the Clown Prince's case, Batman.
2 Golgius (Seven Deadly Sins)
Golgius was a member of the Weird Fangs and a knight in service to Liones. As his crooked metallic visage suggests, he shares many of the Joker's underhanded tactics when fighting stronger opponents.
Instead of battling them directly, he prefers to poison them and remain invisible, savoring every agonizing moment before his prey succumbs to their afflictions. This was a strategy redolent to what the Clown Prince prefers against the likes of Batman and the Justice League since he is not physically capable of defeating him through his own merit.
1 Mayuri Kurotsuchi (Bleach)
Mayuri Kurotsuchi was a Gotei Captain and perhaps the most morally reprehensible among an already questionable group—save for Kenpachi Zaraki and formerly Aizen himself. He shares the Joker's sadistic glee in torturing his opponents and has no regard for the sanctity of life or nature, demonstrated through his experimentation on the Quincies.
Moreover, his Zanpakuto secretes a paralyzing gas that affects ally and enemy alike, one deployed liberally on the battlefield. This is akin to the Joker's laughing gas, both weapons that their respective users are mysteriously immune to.