Several MCU Phase 4 villains have been created by the actions of the beloved heroes themselves. Some were born directly from their actions, while others were created as an answer to them. Thus far, it appears that this may be a common, recurring theme in Phase 4 - as it is indeed also a reoccurring trait of many Marvel villains' origin stories.
Though the MCU ended an era with Ironheart.
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All things considered, it’s clear that while all the Phase 4 movies and shows explore new aspects of the MCU, many of the biggest problems the heroes are now facing have originated from the events of the Infinity Saga. Here’s every known MCU Phase 4 villain that was inspired by the heroes, and what makes said hero responsible.
Baron Zemo
The conflict in Sam Wilson and Bucky Barnes broke him out of prison. Although Zemo showcased his heroic side to help Sam and Bucky fight the Flag-Smashers, he isn't someone who should be easily trusted. Based on his evident lack of concern while imprisoned at the Raft, it wouldn’t be a surprise if Zemo comes back in the future as an even more dangerous villain — perhaps leading the Thunderbolt this time.
The Flag-Smashers
The Flag-Smashers were formed as a direct consequence of Avengers: Endgame's Blip, brought on by the five-year period between Thanos and Hulk's snaps. The Flag-Smashers saw a unified world when the Mad Titan eliminated half of all life in the universe, and they fought to keep it that way. Although they started as a rebellious group with a somewhat noble cause, they soon transformed into a full-fledged terrorist group. Unlike her comic book counterpart, Karli Morgenthau wasn't as interested in fighting Captain America or his allies as much as she wanted to spread her message. It could be said that the Hulk's snap is what originated the Flag-Smashers, but it would be more accurate to say that the collective effort of all of the Avengers brought back those who had vanished along with a new set of problems.
Kang the Conqueror
Although the Avengers' Time Heist in Avengers: Endgame was witnessed by the Time Variance Authority, it didn't have much of a negative impact on the flow of time. Loki instead revealed that the Sacred Timeline had been judged, regulated, and steered by the mysterious Time-Keepers until Ant-Man and the Wasp: Quantumania.
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Hank Pym's Yellowjacket
The What If...? episode 3, all of the candidates for the Avengers Initiative start dying without an apparent reason. It's then revealed that an evil Hank Pym has used the Yellowjacket suit to assassinate the original Avengers in order to get even with Nick Fury, who he blames for the death of his daughter Hope van Dyne. In this universe, Hope died while working for SHIELD, and although Nick Fury isn't really to blame for it, Pym believes that sabotaging his plans is the best retribution. As a result of Hank Pym's successful revenge, Loki invades Earth sooner than expected.
Abomination
Tim Roth’s Emil Blonsky transformed into the MCU’s Abomination in Tim Roth's character will appear in She-Hulk, where he will possibly reunite with Bruce Banner and meet with the MCU's new Gamma-powered hero, Jennifer Walters.
Xialing's New Ten Rings
It may not be entirely clear what her future in the MCU will be, but Shang-Chi's post-credits confirmed that the Ten Rings would return. That presumably means that Xialing will head the new incarnation of the organization in the wake of her father's death. And while Wenwu obviously played a major part in her turn from heroic-aligned warrior to potential future villain - a path she's evidently already on - Shang-Chi himself also helped contribute. His decision to flee from his father and abandon his sister left her feeling isolated and resentful, and determined to show her worth to her father. He may have had no choice, but his decision directly led to the transformation of his sister that will result in the siblings coming into conflict in future.
Marvel's Zombies
What If...? episode 5 introduces the beloved Marvel Zombies storyline to Phase 4 and while the cause of the virus is the Quantum Realm, it would never have spread into the healthy brains of Earth's residents without Avenger-involvement. First, Janet Van Dyne found herself trapped in the Quantum Realm, becoming patient zero and then the attempts to bring her back led to the first wave of infections. It was love and fear over Janet's fate that doomed the world to be overrun by zombies.
Killmonger's Wakanda
Phase 3 already showed what war would do to Wakanda when Thanos' army invaded to fight the Avengers, but Phase 4 goes a step further in What If...? by reintroducing Eric Killmonger (Michael B Jordan) after his Black Panther death. Gifted Tony Stark's resources after tricking the hero into backing him with a Gundam army, Killmonger runs amok, killing T'Challa, Rhodey, and Iron Man himself before taking over Wakanda and waging war against America. In helping Killmonger, even against the better judgement of Pepper Potts, Tony ignorantly equipped his enemy with an army even Wakanda's technology couldn't create, and directly led to him being given the Heart Shaped Herb. In effect, Tony overlooked the consequences - again - and created whatever Avengers team emerges from his death with their greatest enemy.
The Deviants
Hulk's Snap in Avengers: Endgame, as the energy it awakened caused an impending catastrophe called the "Emergence." It's still unknown what this "Emergence" entails, but it could refer to the rise of the Deviants as a direct result of the Avengers' successful Time Heist from Avengers: Endgame.
Gorr the God Butcher
In Marvel Comics, Gorr the God Butcher was an alien warrior from a distant planet who blamed his personal tragedies on the inaction of the gods. In Gorr the God Butcher despises so deeply. Something they may or may not have done in the past could have a lot to do with why he becomes known as the “God Butcher.”
Armor Wars’ Villains
Marvel hasn’t revealed who War Machine will be fighting in Armor Wars, but the source material gives viewers a good idea of what to expect. In the original “Armor Wars” event, Tony Stark was up against people who were using his stolen armor designs. In the MCU show, it will have to be War Machine who takes Iron Man’s place in the story to stop his technology from being misused. Nevertheless, the void Tony Stark has left in the MCU will result in the birth of potential villains who may attempt to replicate Stark’s designs. Some of these new armored antagonists could be Titanium Man, Firepower, Beetle, and the Crimson Dynamo, just a few of the villains created by the actions of heroes in Phase 4 of the MCU.
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