Wonder Man is considered one of several classic Avengers. Many have joined the ranks of Earth's Mightiest Heroes, but Simon Williams has a deep connection to the team, going back to his first appearance in 1964's Avengers #9, by Stan Lee and Jack Kirby.
This made things all the more surprising when Wonder Man turned on the Avengers.
As a classic Avenger, Wonder Man was a fairly frequent member of the team for years, all the way up until 2004's Avengers #500-503, by Brian Michael Bendis and David Finch. The events of "Avengers Disassembled" ended the traditional Avengers, after the Scarlet Witch's breakdown and the resulting death of several Avengers. This was especially hard on Wonder Man, who was still with the team until their disbandment.
Outside of the Vision, Simon might have been the closest to Wanda Maximoff, making her breakdown all the worse for him. It didn't help when Wanda vanished in 2005's House of M #8 by Brian Michael Bendis and Olivier Coipel. Despite this hardship, Wonder Man rejoined the Avengers in 2007's Mighty Avengers #1, by Brian Michael Bendis and Frank Cho.
Fighting beside friends like Carol Danvers and Janet Van Dyne, Simon was fairly happy on the Mighty Avengers. Even so, things weren't exactly like they were before. Wonder Man reached his breaking point when the Wasp seemingly died in 2008's Secret Invasion #8 by Brian Michael Bendis and Leinil Francis Yu.
During an interview in 2009's New Avengers #51, by Brian Michael Bendis, Chris Bachalo and Billy Tan, Wonder Man expressed his disillusionment with the Avengers. Simon talked about how the Avengers used violence to cause nothing but death, which is why the Wasp was seemingly dead and Norman Osborn was in charge of national security at the time. As bad as this was, Wonder Man had only begun his significant vendetta against the Avengers.
Nothing had changed by 2010's Avengers #1, by Brian Michael Bendis and John Romita Jr., when Steve Rogers tried to recruit Wonder Man onto his new Avengers team. Simon still blamed every major disaster on the Avengers, claiming that all they do is cause trouble. Wonder Man also tried to get Steve to shut down the Avengers before it was too late.
When Steve didn't listen, Wonder Man attacked Avengers Tower. Teammates such as Iron Man and Thor were confused by Simon's drastic change of heart. Iron Man suggested that Wonder Man was mentally unstable, especially since he was leaking ionic energy and losing control of his physical form.
Despite his resentment for the Avengers, Simon did help them track down the Scarlet Witch in 2010's Avengers: The Children's Crusade #3, by Allan Heinberg and Jim Cheung. While finding Wanda was certainly nice for Simon, he still hated the Avengers. In 2011's New Avengers Annual #1, by Brian Michael Bendis and Gabriele Dell'Otto, Wonder Man formed the Revengers, a team of heroes with a vendetta against the Avengers.
The Revengers leveled Avengers Mansion before holding a press conference where Simon aired his grievances against Earth's Mightiest Heroes. Fortunately, Iron Man contained Wonder Man so the rest of the Avengers could take down the Revengers. During his time in captivity, Wonder Man revealed his trauma, stemming from his death back in 1994's Force Works #1, by Dan Abnett, Andy Lanning and Tom Tenney, and his strange resurrection in 1998's Avengers #2, by Kurt Busiek and George Perez.
When Wonder Man was resurrected, the Scarlet Witch summoned him in his ionic form, making Simon fear that he wasn't real and that he'd truly died years ago. This traumatic ordeal was a big factor in his hatred and resentment of the Avengers. Fortunately, by 2012's Avengers #34, by Brian Michael Bendis, Brandon Peterson, Mike Mayhew, Terry Dodson, Mike Deodato, Walt Simonson, Leinil Francis Yu, Jim Cheung and Olivier Coipel, Wonder Man had seemingly recovered both physically and mentally.
Simon went to the micro-verse with his fellow Avengers to save the Wasp. This adventure cemented Wonder Man's reconciliation with his old team. By 2013's Uncanny Avengers #5, by Rick Remender and Olivier Coipel, Wonder Man rejoined the Avengers officially. Simon still refrained from violence, maintaining a pacifistic philosophy. Even so, Wonder Man reconciled with the Avengers, putting years of trauma and resentment behind him.