A fictitious antihero team called the Thunderbolts first appeared in American comic books published by Marvel Comics. The majority of the team is made up of former supervillains.Kurt Busiek and Mark Bagley invented the Thunderbolts, who made their debut in The Incredible Hulk #449 (January 1997). When the Avengers were pronounced dead during the events of the 1996 “Onslaught” crossover, the Thunderbolts were initially introduced to readers and the Marvel Universe as a squad of superpowered characters who turned into heroes to aid in defending the planet. But a shocking revelation well-guarded by Marvel came on the last page of their debut comic book issue: the Thunderbolts were, in fact, the Masters of Evil in disguise.

In subsequent storylines, the group rejects their leader Baron Helmut Zemo and attempts to become heroes in their own right, eventually under the leadership of the Avenger Hawkeye. Themes of redemption and the nature of heroism are often featured in Thunderbolts comics. The book has also garnered critical praise for its use of secondary characters from other Marvel Comics and its use of continuity-themed storytelling. The Thunderbolts was an original concept created for Marvel by Busiek and Bagley. Most of the characters used in the final concept were reimagined versions of existing Marvel characters, with additional original characters for the series developed by Busiek and designed by Bagley. The pair also created the new heroic identities for the Masters of Evil. Busiek recalled:

The actual origin of Thunderbolts came when I used to live in New Jersey and drive to New England to visit my parents. To keep myself awake, I’d give myself books to write, and work out about two to three years of continuity. One trip, I assigned myself Avengers, and came up with the plan that the Masters of Evil would ultimately conquer them by posing as new heroes and slowly replacing them. At the time, I thought it was a neat idea, and filed it away.