Warning: The article may contain depiction of violence from movie clips.
Elizabeth Olsen, who recently played the Scarlet Witch, talked about her character's MCU future, feeling hopeful but unsure about a return. Of course, fans recall the Scarlet Witch's most damning and darkest moments in Doctor Strange in the Multiverse of Madness, killing many people and messing with the multiverse before redeeming herself in the final act.
Though the Scarlet Witch did the unthinkable, considering her history as an Avenger, she is not the only Avenger with flaws. Even when Earth's Mightiest Heroes have rescued the planet from various threats throughout the years, they also endured their lowest points, from creating a genocidal Ultron to undergoing an underworld killing spree. Many of these superheroes have indeed engaged in several dark activities that actually call their heroism into question.
Scarlet Witch - Killing the Illuminati
After being corrupted by the Darkhold in Multiverse of Madness, the Scarlet Witch embarked on a lethal trip through the multiverse to find a universe where she could be with her children. After the Illuminati on Earth-838 threatened to stand in her way, Wanda wiped out the organization single-handedly and gruesomely, with each member of the Illuminati's brutal death leaving the audience shocked and terrified.
This moment proved to be the darkest that Wanda Maximoff ever got, as she knowingly ripped apart Earth-838's heroes, even after learning that one of them was a father. She executed each of these superheroes with maximum prejudice and without hesitation, cementing her fall into villainy.
Spider-Man - Trying To Kill Norman Osborn
Peter Parker lost everything by the end of Spider-Man: No Way Home, but the death of his Aunt May was what finally pushed him over the edge. After getting the chance to battle May's killer, Norman Osborn, Peter made it very clear that he intended on killing the supervillain, only for his alternate-reality variant to stop his killing blow just in time.
This was the only moment since Peter Parker's introduction into the MCU where the hero proved himself willing to take another human being's life. As a hero that is normally adamantly opposed to killing, this scene showed just how broken he was following May's death.
Bucky Barnes - Killing The Starks
Bucky Barnes may have once been a war hero, but his years thereafter as a Hydra assassin sought to erase any heroism from Bucky's soul. His most infamous mission was revealed in Captain America: Civil War, with footage showing his brutal murders of Howard and Maria Stark.
Though Bucky was brainwashed by Hydra at the time of these killings, the deaths of the Starks weigh no less heavily on his shoulders. These deaths proved even more painful to the man known as the Winter Soldier because of his history with Howard Stark, whom he had worked alongside during World War II.
Hulk - The Johannesburg Rampage
Bruce Banner fosters a healthy fear of his Hulk persona primarily for reasons displayed in Age of Ultron. After being mind-controlled by Wanda Maximoff, the Hulk goes on a rampage through the streets of Johannesburg, wreaking destruction like never before and laying waste to various corners of the city.
Though Hulk wasn't in his right mind during this rampage, it is made plain that both he and Banner deeply regret what happened. This sequence of events led the Avengers to lay low in preparation for their upcoming fight against Ultron, while also later informing the Hulk's decision to leave the planet at the end of the film.
Hawkeye - One-Man War On Crime
After the Snap left Clint Barton without his wife and children, the Avenger formerly known as Hawkeye went down a dark path. No longer interested in preserving life, Clint adopted the moniker of Ronin and began a one-man killing spree, wiping out different gangs from around the world in his quest for vengeance.
Though Clint's rage was specifically directed at the worst kinds of people, it was ultimately misplaced, as he sought vengeance against humanity for Thanos's misdeeds. The many deaths on his hands would come back to bite him during the events of Hawkeye when certain victims retaliated against the Avenger and his new partner.
Black Widow - "Killing" Dreykov's Daughter
Natasha Romanoff was not always the heroic Avenger who fans have come to know and love today. In fact, as the flashbacks depicted in Black Widow, she was once a callous assassin under the control of General Dreykov. In order to free herself of Dreykov's power, however, Natasha was forced to kill both him and his young daughter in an explosion.
Though it is later revealed that both Dreykov and his daughter survived the explosion, this moment clearly haunted Natasha for the rest of her life. Even if she hadn't really taken the child's life, she had been willing to, and such a reality stole a piece of her soul that never truly recovered. Natasha would spend the rest of her life trying to atone for this callous action.
Doctor Strange - Possessing His Dead Variant
Doctor Strange in the Multiverse of Madness pushed the eponymous Master of the Mystic Arts to his breaking point as he faced off against the villainous Scarlet Witch. Trapped in an incursion-torn universe, Strange utilized an incantation from the Darkhold to dreamwalk into his alternate self, a deceased variant buried on Earth-616, to engage in one final battle with Wanda Maximoff.
The final shot of the film may prove this to be one of Doctor Strange's worst decisions in the MCU, as a mysterious third eye protrudes from the sorcerer's forehead as a result of his diving into dark magic. The spirits of the damned had warned him that there would be consequences for his actions, but he failed to listen and now must pay the price.
Thor - Beheading Thanos
Audiences found Thor at his very lowest in Avengers: Endgame after he failed to stop Thanos from wiping out half of all life in the universe. When the remaining Avengers tracked the Mad Titan down to his farm on a distant planet, Thor wasted little time before beheading his archenemy with Stormbreaker, killing him.
From this moment on, Thor would sink into a lengthy depression as a result of his failures. His execution of Thanos did not compensate for his shortcomings in Infinity War, but indeed only made things worse. This proves to be one of Thor's darkest moments, one that he must still strive to overcome when he returns in Love and Thunder, one of the summer's most exciting new movies.
Captain America - Almost Killing Tony
Though it doesn't quite capture the enormity of the comics event, Captain America: Civil War perfectly rips the Avengers apart from the inside. The largest division comes between Captain America and Iron Man, who come to blows after Tony learns that Cap protected his parents' murderer for years. Cap wins the fight, but in his rage, nearly kills Tony with the very shield his father had given him.
As he stood over Tony, Cap realized that he had lost the moral high ground that made his fight against the Accords worth ripping the Avengers apart. Knowing he had made a mistake, he willingly left his shield behind with Tony, giving up the mantle of Captain America, which he would not take up again until the events of Endgame, almost seven years later.
Iron Man - Creating Ultron
Tony Stark is an Avenger with many demons, not the least of which includes his colossal miscalculation when it came to the invention of Ultron. Though he intended on creating something that could protect the Earth even better than the Avengers could, Tony ended up forging one of the worst threats the world had ever faced.
This failure on Tony's part would inform the next phase of his character development, as he sought to make up for his mistakes. He would go on to support the Sokovia Accords as a way to regulate himself and the other Avengers, thereby keeping them from creating anything like Ultron ever again. The creation of Ultron may indeed have been Tony's biggest failure in his career as an Avenger, and one that he never fully forgave himself for.