Source: nerdist.com

7. Angel/Archangel

X-Men, X-Factor - Marvel Comics

X-Men change sides like"¦well, like X-Men change costumes. But most of that is villains becoming heroes, not the other way around.

However, we do have the story of Angel. Original X-Man Warren Worthington, III stayed on with the team for some time. Then, after a brief stint with the Champions, he returned to New York to found X-Factor with his old X-teammates and his college roommate Cameron Hodge.

But Hodge secretly hated Warren and wanted him dead. So, when Harpoon heavily damaged Warren’s wings during the Mutant Massacre, Hodge took his chance. He convinced the doctors to amputate Warren's wings, which eventually drove Warren to attempt suicide. Apocalypse saved him, gave him new metal wings, and set him up as his Horseman of Death. Warren fought the X-Men until they managed to break his conditioning and bring him back to their side.

And Hodge? He was decapitated"¦by metal wings.