One of the most common causes of death in the Marvel Universe is The Infinity Gauntlet. Its during the miniseries of the same name that space bad guy Thanos wields the reality-warping weapon and erases half of the life on the universe, which includes Spider-Man, Daredevil, and most of The Fantastic Four along with billions of others. The mad titan wasnt the only one to pull that trick, though. Its just that people try not to spend too much time remembering The Onslaught Saga, an X-Men crossover from the mid-1990s which saw a powerful psychic villain laying waste to the worlds superheroes...only for it to transpire that the villain is Charles Xavier, fused with bad parts of Magnetos mind. Eventually everything goes back to normal, but there was a time when Onslaught did the erased from reality thing on the Fantastic Four and most of the Avengers, too. In that case it was a backdoor introduction to a new Marvel initiative a few months later, Heroes Reborn, where Captain America and the rest returned in redesigned costumes.