TheMarvel Cinematic Universewas first introduced with Iron Man in 2008. In the following 15 years, throughout the MCU, redemption has been a recurring theme when it comes to a character’s individual arc and development. While the antagonist of each story are often the driving force, there have been times when they have turned into the protagonist by the end.
Related:Victim or Villain?: MCU Villains Who Blurred the Line

While some characters gradually change, others’ make quick decisions that change the trajectory of their life and thus, dictate who they are and who they become. These are the top contenders of antagonists turned protagonists in the MCU films.
10Darren Cross
Darren Cross (Corey Stoll) was introduced as the main antagonist in Ant-Man. Obsessed with the Pym Particle, Darren took extreme measures with the hopes of weaponizing it for profits. Having created a weaponized suit he called the Yellowjacket, Scott Lang was forced to sabotage the wiring of his suit, shrinking him to subatomic size.
Although it was believed that he died in the Quantum Realm,Ant-Man: Quantamaniarevealed that he survived, transforming himself into MODOK, a weaponized killer. Although Darren continued his ruthless behaviour in the Quantum Realm, until Cassie appeals to him, leading him to fight against Kang. Although Darren was not a conventional hero, he fought for the greater good, and died thinking he was an Avenger.

9Otto Octavius
Otto Octavius (Alfred Molina) was the main protagonist inSpider-Man 2. He was a widely acclaimed scientist until his scientific experiment went wrong. Otto suffered damage in this accident and as a result, the tentacle-like arms took control of his body.
Arguably, Otto himself is not a villain as his higher brain functions were inhibited. However, inSpider-Man: No Way Home, as soon as he is given the control back, Otto is able to regain control of the tentacles and rectify his mistakes. In the final battle, he is seen fighting alongside Spider-Man to stop the remaining antagonists.

8Quicksilver
Pietro Maximoff (Aaron Taylor-Johnson) was introduced inAvengers: Age of Ultronas a leading antagonist working with HYDRA. After undergoing experimentation that gave him enhanced abilities, Quicksilver was driving force for the Avenger’s failure to stop Ultron initially.
While both Pietro and Wanda’s reasons for supporting Ultron was a personal grudge against Tony Stark, they both realize who the bad guy really is after discovering Ultron’s genocidal plans. Not only did Quicksilver join the Avenger’s fight to save Sokovia,he sacrificed his lifefor Clint Barton, his ally Avenger.

Wenwu (Tony Leung) was introduced inShang-Chi and the Legend of the Ten Ringsas a ruthless leader who sought power and control. Although Wenwu was a villain for the larger portion of his life, all he really needed was a change of perspective, which is offered through Ying Li’s affection and companionship. After he loses her at the hands of his enemies, Wenwu is overcome with grief, leading him to reclaim his prior life.
When he sees a chance to bring her back and complete his family, he doesn’t hesitate to take drastic measures. After unleashing the Dweller in Darkness, he realizes what he has done. In his final moments, he gives up the Ten Rings, and with it, his life, choosing to save his son instead.His sacrifice for Shang-Chi meant he died with the title of a hero.

6The Winter Solider
Bucky Barnes (Sebastian Stan) was initially seen inCaptain America: The First Avengeras Steve Roger’s best friend. After he seemingly falls to his death, it is later revealed that Bucky did not die but was rather kept alive, brainwashed, and armed as a professional assassin called the Winter Solider.
Although Bucky was the vessel for villainous actions, Bucky himself was a victim of HYDRA’s ill-intent. Bucky chose to remain in a cyrogenic sleep until a cure for his brainwashing is established, demonstrating his selfless nature. Bucky was able to regain control of his life after Shuri cures him. In the end, Bucky turned the title of the Winter Soldier from a villain that sows fear to that of a hero that holds hope.
5Adam Warlock
Adam Warlock (Will Poulter) was a weapon created by the Sovereign designed to kill the Guardians of the Galaxy in the third film. Tasked by his mother Ayesha and the High Evolutionary, Adam did what he was told instead of acting out of free will.
Despite his repeated attempts to kill the gang, Groot saves his life, stating that everyone deserves second chances. Groot had a huge role in changing the trajectory of Adam’s life as he then saved Star-Lord’s life, redeeming his character arc. Guardians of the Galaxy 3 ended with Adam joining the gang,marking the start of the character arc of a hero.
Yondu (Michael Rooker) was first seen in Guardians of the Galaxy as the Ravager who kidnapped Peter Quill, ultimately keeping him in his care. Despite being introduced as a villain who not only abducted children from Earth for money, his love and care for Peter kept him grounded in doing the right thing.
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In the second film, Yondu tries his best to rescue Peter from Ego. He admitted he kept Peter, not for his own benefit, but because he believed handing him over would cause Peter harm. Although Yondu was established as an anti-hero, he was never truly a villain, but rather a misguided protagonist in the making.
3Wanda Maximoff
Wanda Maximoff (Elizabeth Olsen) was first seen working alongside Ultron until she saw his true intentions, leading her to switch sides. She fought alongside the Avengers as a protagonist until the grief of losing Vision led her to create a false reality in the town of Westview. Upon realizing what she had done, she relinquishes, giving up her family once again.
Related:MCU: 10 Characters Who Paid the Price of Being a Hero
However, inDr. Strange 2, Wanda continues her dangerous pursuit for her children in alternate universes. Although her actions of mass murder paint her as a malicious villain, proving Wanda is capable of being a dangerous force to be reckoned with, Wanda is a good person at heart. Irrespective of the mistakes she has made and the decisions that steered her away from what’s right, Wanda has been a selfless hero on more than one occasion demonstrating that she is a hero worthy of praise.
Loki (Tom Hiddleston) was initially seen as a jealous brother competing with Thor seeking the throne of Asgard. He was initially overwhelmed after finding out he was adopted, seeking his father’s acceptance he realized that Odin spent his life grooming Thor for leadership, neglecting Loki as he was never meant to be king. Living in his brother’s shadow, Loki became insecure and thus embraced the title he did recognize to be true- the God of Mischief, projecting chaos as a villain.
Related:10 Marvel Villains Who Actually Succeeded in their Goal
However, inThor: Ragnarok, Loki fights alongside Thor to save Asgard from Hela. Similarly, he risked his life at the hands of Thanos, ultimately paying with his life. In the tv show, Loki witnessed how his life played out, leading him to question his life’s decisions. As a result, his impulsive chaotic nature was put in check as he carefully contemplated the dire consequences of killing He Who Remains.
Nebula (Karen Gillian) was introduced inGuardians of the Galaxy, working alongside Ronan in his pursuit for the Power Stone. Despite being fully aware of Ronan’s genocidal plans, she continued to support him, being an instrumental role in his possession of the Power Stone in the first film.
However, as soon as Nebula was given the opportunity to escape her father, she ceased her criminal activity, seeking nothing more than to stop her father’s genocidal plans. As a result, it became evident that Nebula was never malicious but rather, a victim of her circumstances. In her first versus most recent on-screen appearance, Nebula has matured into a hero, where inGuardians of the Galaxy 3, she was seen fighting alongside the other members against the High Evolutionary.