Kevin O'Neill was among the first artists of 2000 AD, and he is best known as the co-creator of 'Nemesis the Warlock', 'Marshal Law' and 'The League of Extraordinary Gentlemen'. One of his first jobs was for the IPC company, where he worked at the offices of the Buster children's magazine. From 1976, he was a colorist for other children's publications. When IPC launched the science fiction title 2000 AD in 1977, O'Neill was among the earliest cooperators.
For 2000 AD, O'Neill illustrated the cover of the first issue, and later on, comics like 'Tharg the Mighty', 'Future Shocks' and several humorous stories. With writer and editor Patt Mills, he eventually created the 'Ro-Busters' series. O'Neill continued to work with Mills on projects like 'Nemesis the Warlock'. O'Neill also illustrated stories with 'Judge Dredd' and the 'ABC Warriors'.
By the early 1980s, O'Neill became a freelancer and did work for DC Comics. He did fill-ins on 'The Omega-Men' and cooperated with Alan Moore for the first time on a story in 'Tales of the Green Lantern Corps Annual', which even got him in trouble with the Comics Code Authority. At DC, he also published the graphic novel 'Metalzoic', another collaboration with Pat Mills. O'Neill and Mills then began the superhero satire 'Marshal Law' at Epic. It was later transferred to Apocalypse Comics and Dark Horse, and also became a weekly comic called 'Toxic!', with Marshal Law as the main character.
In 1999, he worked with Alan Moore again. O'Neill and Moore created 'The League of Extraordinary Gentlemen', which featured various characters from Victorian literature. The comic was a big success, and turned into a feature film in 2003.