Joker

The Joker is a supervillain and the archenemy of Batman. He was first introduced in Batman #1 (Spring 1940) and has remained consistently popular. The Joker is a master criminal with a clown-like appearance, and is considered one of the most infamous criminals within Gotham City. Initially portrayed as a violent sociopath who murders people for his own amusement, the Joker later in the 1940s began to be written as a goofy trickster-thief. That characterization continued through the late-1950s and 1960s before the character became again depicted as a vicious, calculating, psychopathic killer. The Joker has been responsible for numerous tragedies in Batman's life, including the paralysis of Barbara Gordon (Batgirl/Oracle) and the murders of Jason Todd (the second Robin) and Jim Gordon's second wife Sarah Essen.

The Joker with Harley Quinn

A different Joker and Harley

The Joker with Poison Ivy and the Penquin