O’Neil was best known for his work on Batman, which included writing Batman, Detective Comics, and Batman: Legends of the Dark Knight, as well as editing DC’s Batman titles from 1986 to 2000. He, editor Julius Schwartz, and artist Neal Adams are credited for guiding the Dark Knight back to his darker roots after a period of campiness brought on by the success of the 1960s Batman TV series.
Also at DC, he wrote the iconic Superman vs. Muhammad Ali one-shot, the Armageddon 2001 event, as well as memorable runs on Justice League and the Question.
The writer also branched out to TV, writing episodes of Logan’s Run, Superboy, Batman: The Animated Series, and G.I. Joe: A Real American Hero.