Wonder Man

Simon Williams was an industrialist's son who took a bad deal with Baron Zemo, was transformed into a superhuman weapon, and died in his very first appearance after turning against the Masters of Evil to save the Avengers. It should have been the end of him. Instead his brain patterns were recorded and used to give the Vision a personality, which makes Wonder Man the single most structurally important dead character in Avengers history.

He came back as an ionic being, joined the team for real, and reinvented himself as a working Hollywood actor, which gave Marvel a rare superhero with a genuine day job and an agent. He has died again, returned again, briefly turned against the Avengers as leader of the Revengers, and been written as a pacifist so committed that he refuses to punch. Nathan Fillion is playing him in an upcoming Disney+ series that leans hard into the Hollywood angle.

Stan Lee and Don Heck created Simon in The Avengers #9 in 1964 and killed him in the same issue. Roy Thomas then used his recorded brain patterns to give the Vision a mind, an act that made the Vision, the Scarlet Witch and Wonder Man permanently entangled.

Simon returned in the 1970s as an ionic being, joined the Avengers properly, and became a West Coast Avengers fixture with a Hollywood acting career, a genuinely fresh angle for a superhero at the time.

Later runs have leaned into his instability: he has died and reformed repeatedly, adopted absolute pacifism, and led the Revengers against the Avengers in 2011 out of a sincere belief that the team causes more harm than it prevents.