Avengers: Doomsday will include some of the strongest Marvel villains in the MCU's roster, headlined by Robert Downey Jr.'s Doctor Doom. The upcoming crossover event will assemble a massive ensemble of heroes, which includes characters from the Avengers, X-Men, and the Fantastic Four, as they unite against Doom to save the Multiverse.
While Doom is the overarching big bad, Avengers: Doomsday is filled with former villains who will join on the side of good this time around, and one unstable character who could be exploited by Doom to level the playing field.
Avengers: Doomsday is set to premiere in theaters on December 18.
Avengers: Doomsday Unveils 4 of Marvel's Strongest Villains
Doctor Doom
At the center of the conflict in Avengers: Doomsday is Doctor Doom, who is confirmed to have evil plans for the Multiverse, the reasons for which are unknown. Doom is no doubt one of Marvel's smartest and most ruthless characters, mainly due to his dangerous collection of skills and powers.
Aside from his genius-level intellect and unbreakable willpower, Doom has immense mastery of sorcery, time travel, and manipulation. Doom also has a whole nation of loyalists in Latveria at his disposal.
As a villain who is capable of outsmarting and outpowering most of Marvel's heroes (combined with the fact that he became God Emperor Doom at one point in Marvel Comics), Doctor Doom is perhaps the strongest villain that the Avengers will face in Doomsday.
Magneto
While Magneto is not the main villain in Doomsday, a May 2025 rumor claimed that the Avengers and the X-Men would be pitted against each other, possibly due to Doom's manipulation. By being on the other side of the battle, Magneto is dangerous as an enemy, considering that he is an Omega-level mutant who can manipulate metal to the fullest extent and cause massive destruction. Still, Magneto will eventually be an ally.
Magneto's return in Avengers: Doomsday will officially fulfill a 26-year-old X-Men dream, according to a report claiming he will achieve a "mutant utopia" he has always dreamed of. Magneto will join the fight against Doom because the same report revealed that Robert Downey Jr.'s villain in Doomsday will threaten the utopia that he worked hard to build.
Loki
Loki was once a villain, considering that he was responsible for assembling the Avengers in the first place during 2012's Battle of New York in The Avengers. However, he has since changed, mainly because he is now God Loki (aka the Multiverse's guardian) in Avengers: Doomsday.
As God Loki, he is immensely powerful, especially after receiving upgrades, such as time-slipping expertise and reality-warping from Loki Season 2. This is on top of her Asgardian godhood and master trickery.
The Void
The Void is the destructive alter-ego of Sentry, who engulfed New York in darkness and placed everyone in mental shame rooms in one go during the events of Thunderbolts*. While Sentry is already an ultra-powerful hero, his transformation into the Void gives him a scary upgrade because he becomes an entity who can wipe out entire teams or planets whenever he pleases.
Given that the Void is unstable, Doom could use this trait as an advantage for himself and turn the Void into his ally to weaken the Avengers, X-Men, and the Fantastic Four. While Doctor Doom is considered the strongest due to the perfect combination of his skills and traits, the Void is right up there in the list due to his unpredictability and unstable nature.
