Kavanagh was a Marvel Comics editor from 1985 to 1997. Titles he edited during that time included Marvel Comics Presents and Nick Fury, Agent of Shield. In 1987, he began to write for Marvel with his first published story "Cry Vengeance!" appearing in Kickers, Inc. #4 (Feb. 1987). He later wrote such titles as Marc Spector: Moon Knight, Avengers: Timeslide, X-Man and X-Universe. In Web of Spider-Man #100 (May 1993), Kavanagh and artist Alex Saviuk gave the lead character "Spider-Armor". He wrote the Spider-Man/Punisher/Sabretooth: Designer Genes one-shot the following month. Kavanagh was one of the writers on the "Maximum Carnage" storyline which ran through the various Spider-Man titles in 1993. The first Black Cat limited series was co-written by Kavanagh and Joey Cavalieri in 1994. Kavanagh pitched a storyline involving the return of Spider-Man's clone, which then formed the basis of the "Clone Saga" which began in Web of Spider-Man #117 (Oct. 1994). Kavanagh's last new comics project was the Before the Fantastic Four: The Storms limited series in 2000–2001.In 2011, Kavanagh co-founded the internet startup company www.mybeanjar.com.

This tells the story of the X-Men's greatest villain Apocalypse, or En Sabah Nur as he was known in ancient Egypt. Witness his rise to power and the challenges he faced in his attempts to fulfill his dream of world domination.