10 Marvel Supervillains Who Almost Destroyed The Avengers

Ever since he was initially created by Hank Pym as a defense protocol in Avengers #54, Ultron has remained a constant thorn in the side of the Avengers. Generally speaking, he is one of the most persistent and prevalent villains throughout comics history. He's been coming this close to defeating the Avengers regularly for the past five decades now, but at no point did he come quite as close to besting the whole team as in the Age of Ultron run.

In this story, set in the not-too-distant future, Ultron has defeated the Avengers so thoroughly that he has now taken over the planet. Ultron sentinels patrol the streets, hunting for any remaining superheroes. A ragtag amalgamation of remaining Avengers, Defenders, X-Men, and members of the Fantastic Four all formulate a plan to use Doctor Doom's Time Platform to travel to the future to stop Ultron. Wolverine, however, forms a plan of his own, traveling backward in time to kill Hank Pym before he ever makes Ultron.

This leads to a lot of time-traveling hijinks, including Wolverine eventually having to go back to stop himself from going back to kill Hank Pym. Ultimately, he and Sue Storm convince Pym that he must still build Ultron but to put in a secret fail-safe. This change in Ultron's history allows the Avengers to then defeat him before he is ever able to take over the world.

So while he may not have technically defeated the Avengers in the long run, it's only because they cheated the space-time continuum, repeatedly.