Azzarello is best known for his numerous collaborations with artists Eduardo Risso (100 Bullets, Batman: Broken City, Spaceman, Moonshine) and Lee Bermejo (Batman/Deathblow, Luthor, Joker, Batman: Damned), his contributions to the Watchmen prequel project Before Watchmen and The Dark Knight Returns sequel series DK III: The Master Race, as well as for his stints on the long-running Vertigo series Hellblazer and The New 52 relaunch of the Wonder Woman title.

[1] He contributed short stories to a number of Vertigo's anthology titles and penned Jonny Double, a 4-issue limited series which marked his first collaboration with Argentine artist Eduardo Risso.

[4][5] The series ran for one hundred issues, from 1999 to 2009, and was noted for Azzarello's use of regional and local accents, as well as the frequent use of slang and oblique, metaphorical language in his characters' dialogue.

'"[8] The results were the 6-issue Batman: Broken City[9] and the 12-issue "Superman: For Tomorrow", which was supposed to be the centerpiece of a larger storyline consisting of several interconnected mini-series, including one written by Azzarello, Lex Luthor: Man of Steel.

[10][11][12] The initiative, unofficially dubbed "Superstorm" due to the fact that the mini-series were edited by the team of DC's Wildstorm imprint, experienced production problems and delays, causing Luthor to become a standalone work only loosely connected to "For Tomorrow".

[13] In the following years, Azzarello continued to write more Batman-related stories such as the 2008 graphic novel Joker, a serial for Wednesday Comics in 2009[14][15] and Flashpoint: Batman — Knight of Vengeance.

[23][24] In 2014, Azzarello became the co-writer of the weekly series The New 52: Futures End along with Jeff Lemire, Keith Giffen and Dan Jurgens.