While Magneto was originally one of the worst villains in the Marvel Universe as he was backed by a righteous mission in which he believed whole-heartedly, making his villainous deeds that much more dangerous, the Avengers actually battled a villain they believed was even worse than Magneto–a conclusion that was made by a former associate of the Master of Magnetism.
Erik Magnus Lehnsherr aka Magneto made his Marvel Comics debut in X-Men #1 as a solo mutant extremist who fought to cripple humanity and allow mutants the chance to rise to power. A few issues later, it was revealed that Magneto had his own super-villain team known as the Brotherhood of Evil Mutants, and Quicksilver and Scarlet Witch were among its members. However, after working under Magneto as a way to repay the villain for saving their lives years earlier, Scarlet Witch and Quicksilver decided it was time to part ways with Erik and pursue their dream of being superheroes as opposed to the villainous role they were forced to play. So, Wanda and Pietro Maximoff joined the Avengers and defended the Earth from villains as evil as Magneto–and even some who they believed were much worse.
Related: Marvel Confirms the Weakest Avenger isn't Who Fans Think
In Avengers #17 by Stan Lee and Don Heck, the Avengers are searching for the Hulk as they wanted him to rejoin their ranks following the departure of the other founding members. After Thor, Iron Man, Ant-Man, and the Wasp left the team, the Avengers consisted of Captain America, Hawkeye, Scarlet Witch, and Quicksilver. While the Avengers were still a force to be reckoned with, the new lineup lacked a heavy-hitter and they hoped the Hulk would fill that role perfectly. So, the Avengers followed the Hulk’s trail to
Read more on screenrant.com