The Joker is a master criminal with a clown-like appearance, including bleached white skin, red lips, and green hair. Initially portrayed as a violent sociopath, who in his first several appearances, murdered close to three dozen people for his own amusement, the Joker, originally introduced in Batman #1 (1940), began to be written as a goofy trickster-thief. That characterization continued throughout the late 1950s and 1960s before the character was again depicted as a vicious killer, beginning in Batman #251, with "The Joker's Five Way Revenge", the Joker returns to his roots as a homicidal maniac who casually murders people on a whim, while enjoying battles of wits with Batman.
The Joker then received his own nine-issue series during the 1970s in which he faced off against a variety of superheroes and supervillains. Although he was the protagonist of the series, certain issues feature just as much murder as those in which he was the antagonist. Of the nine issues, he commits murder in seven.