The Joker

Another possibly apocryphal tale about the Joker says that he used the same chemicals that transformed him to make two others like himself, and that the three Jokers alternated tormenting Batman over the years, using different approaches. The Criminal, cold and calculated, prioritized crime. The Clown was a showman who enjoyed setting up elaborate set pieces, often involving giant props, in which to battle Batman. The Comedian was the unhinged madman who committed everything to the joke... and the joke was usually horrific and violent. But it's equally possible that these are simply three different facets of the Joker's fractured persona.

Batman defeated The Joker on a number of occasions, resulting in him being sent to Arkham Asylum for the criminally insane, but The Joker didn't seem to mind. During one stay, he managed to get into the head of his psychiatrist, Doctor Harleen Quinzel, to the point that she had a mental breakdown and helped him escape. He took her to the Ace Chemical Plant where he either pushed her or convinced her to jump into the same chemicals that had changed him. She took on the identity of Harley Quinn, becoming The Joker's romantic and criminal partner, though she eventually left when she came to see the toxic nature of their relationship.

The Joker has worked both with and against other villains at times. He's gone to war against the Riddler in the War of Jokes and Riddles. He first teamed up with Scarecrow, but then came to blows with him when The Joker's unpredictable ways exhausted the precise Doctor Crane's patience. The Joker has teamed with Lex Luthor on more than one occasion, including in the Legion of Doom, but both of them seem to do so expecting a betrayal at some point, with the only question being who will do it first. At the end of the day, The Joker is a man who will shoot his own henchmen as a punchline to a quip, so anyone who allies with him expecting true loyalty would have to be crazier than he is... and no one is crazier than The Joker.

The Joker has likely inflicted more pain on the Batman Family than anyone. He shot and paralyzed Barbara Gordon; it's unclear if he knew she was also Batgirl, or if he was just striking at Commissioner Gordon. He murdered the second Robin, Jason Todd. And in caverns beneath Gotham, he fought Batman to the death, though they were both resurrected after plunging into a pit of Dionesium, the active ingredient in the Lazarus Pits that Ra's al Ghul uses to sustain his immortality. It's not clear if The Joker intended to die in battle with his old enemy, or if he knew the Dionesium would return them to life to continue the war he often seems to genuinely enjoy.

The Joker's view of Batman is bizarre. While he clearly enjoys inflicting pain on his nemesis, on rare occasions he has aided Batman against a mutual foe and displayed an almost protective sense of ownership toward the Dark Knight. When Batman and Catwoman planned to marry, The Joker attacked Catwoman, trying to convince her not to marry Batman. Another time, Harley Quinn, seeking revenge on The Joker, placed bomb vests on both him and herself. With both vests on timers, Batman only had time to save one of them. The Joker was confident it would be him, only to feel betrayed when Batman chose Harley. Even so, The Joker always considers Batman his greatest enemy.