The Joker (Earth-31)

The Joker was a psychopathic mass murderer who was confined to a psychiatric facility after the retirement of the Batman.

All-Star Batman and Robin the Boy Wonder
Joker hired the man who murdered the parents of Dick Grayson and planned something large for the Dark Knight.

The Dark Knight Returns
After Batman's retirement, Joker was driven into a state of catatonia for ten years after the disappearance of his old foe. However, once Batman took to the streets again, Joker re-emerged from his catatonia and sought to battle the hero once more. He manipulated his psychiatrist into thinking that he had been cured from his psychopathy. His psychiatrist then managed to get him into a talk show to talk about his new self, but was killed along with everyone in the same room.

Joker then made his way to an amusement park, where Batman arrived and dueled his old foe, promising to end his life. In the battle, Joker managed to shoot Batman in the stomach and stab him there several times, but Batman flung a Batarang into Joker's eye and broke his neck, paralyzing, but not killing him. Batman found himself unable to kill the Joker, to which Joker, out of disappointment, twists his own broken neck while cackling cruelly in order to frame Batman for murder.