10 Comic Book Villains That Died (And Never Returned)
3. Mastermind
The original Mastermind may have been a Lee/Kirby creation, but it was Chris Claremont and John Byrne who really defined the character during their stint on X-Men.
A former member of the Brotherhood of Evil Mutants, Jason Wyngarde is most famous for his role in the seminal Dark Phoenix saga as a member of the notorious Hellfire Club. During that storyline, Wyngarde manipulated the Phoenix entity and played Jean Grey against her former X-Men teammates, utilising his powers of deception to stoke a conflict that neither he nor the X-Men would be able to control.
In the wake of this storyline, and having tried to steal the Phoenix Force for himself, Wyngarde would succumb to the Legacy Virus, a disease born in the future and designed to kill Mutants all over the globe.
He dies having sought forgiveness from Jean for his acts, but it's telling that Wyngarde, unlike other X-foes, has never returned in the comics, especially since he had such a massive part to play in what many would consider to be the group's most famous storyline.