10 Marvel Supervillains Who Almost Destroyed The Avengers

Primarily serving as an X-Men villain, Onslaught was the unwitting brainchild of Professor Charles Xavier and Magneto, quite literally. During a fight between the two when Professor X had gotten into Magneto's mind, some of Magneto's darker tendencies crept into Charles' subconscious and the result was an entirely separate, powerful entity, that came to be known as Onslaught.

During the aptly-titled Onslaught comic event series, the X-Men and the Avengers teamed up in an attempt to stop Onslaught's plan to achieve Charles' wish for peace between mutant and humankind using Magento's most violent and destructive methods.

However, just before he was able to finish this plan, Reed Richard figured out that non-mutant characters could absorb some of Onslaught's powers and leave him vulnerable to attack. This resulted in a huge roster of Avengers and other nonmutant characters becoming one with Onslaught's form and seemingly being killed when the X-Men then attempted to destroy Onslaught.

However, it was later revealed that Franklin Richards had created a pocket universe in which to house all of them to protect them from the blast. Onslaught would eventually return to cause trouble elsewhere, he never came this close to truly killing the Avengers ever again.