With Kevin Fiege announcing that he will be dropping more information about Marvel's next big saga in the coming months, the success of the MCU's Phase 4 villains cannot be overlooked (per ScreenRant).
This phase has been packed with brilliant plot lines, powerful stories, and most importantly, stellar villains. From the plot twist that was Agnes Harkness kicking off phase 4 in WandaVision, to, most recently, Arthur Harrow in the Moon Knight series, it is unquestionable that fans have gotten their fair share of complex, nuanced, and just plain wicked villain stories.
Note: This list focuses on strictly MCU entries, not any of the MCU-Sony collaborations.
The Mandarin
Shang-Chi and the Legend of the Ten Rings remain to be one of the most unique movies because the villain who was set up from the start of the movie, was not truly the villain by the end. Wenwu, the father of Shang-Chi, hears his wife's voice telling him she is trapped in Ta Lo, beautiful land where the locals are keeping Dwellers-in-the-Darkness locked.
Wenwu has every intention of breaking his wife out but is stopped by Shang-Chi who knows the voice is just a call from the Dwellers-in-the-Darkness begging to unleash them. Even though Wenwu was set up as the villain, at the end of the day, Shang-Chi fought the Dwellers-in-the-Darkness during his final battle after beating and simultaneously making up with his father. The villain of this story is not only one who can be sympathized with, but one who, at the end of the day, was not the villain, but rather a man with grief.
Agatha Harkness
Agatha Harkness, aka Agnes Harkness, through the duration of WandaVision, takes advantage of Wanda's vulnerability, and the curse she happened to have cast, to minimally wreak havoc on the people within Westview.
While Agnes's reveal was quite ingenious and sets her up to potentially appear as a villain in future MCU projects, her character did not act as the main villain behind this story. Besides her motive to take Wanda's powers, she still did not play a large role as the antagonist in this series until the show's slightly disappointing finale. Here, even though presented as the villain, Agnes was merely a bystander as Wanda was the true anti-hero of this series.
Karli Morgenthau
Karli is one of the more morally questionable characters in Phase 4. She is neither good nor evil. Her goal throughout Falcon and the Winter Solider was to restore the world to the way it was during the blip. For her, that meant creating equitable housing and healthcare.
Because there were fewer people during the blip, there were more resources for a larger number of people, and items were distributed more equitably to people. However, after the blip, things went back to the way they were. While Karli's beliefs of wanting access to healthcare and housing were morally justified, her actions were not, making her a morally questionable villain.
Arishem
A character who poses a large philosophical question in the MCU was Arishem. He was first introduced to fans during the Eternals and his goal was to expand the universe by creating stars and planets but in doing that, Aishem would sacrifice "lower life forms." When the Eternals found this out, they split into sides: ones that backed Arishem and his plan to destroy Earth, and the ones who were defending the people of Earth.
Aishem is a good villain, just not a great villain, as he was able to divide the Eternals and almost carry out his plan. What makes Arishem a questionable villain is the fact, like Thanos, he posed a philosophical question that had a very cut and dry answer, but still left fans thinking and potentially siding with him by the end.
Arthur Harrow
As seen in one of the best new TV shows, Arthur Harrow, the villain of the Moon Knight series, has the power of Ammit, the Egyptian Goddess of devouring souls. His goal, and Ammit's goal, is to judge souls before they have the power to commit their future evil deeds. This villain also poses a large philosophical question regarding right and wrong, and whether it's appropriate to judge a person before they've committed wrongdoing.
Regardless, Arthur was willing to steal the souls of millions of people, even children, if that meant preventing a crime that would've been done in the future. If Arthur was not stopped by the Avatars of Konshu, the Jewish American and English alters Marc Spector and Steven Grant, respectively, people's souls would've been judged prematurely, an action which would be hard to undo.
Wanda Maximoff
Wanda has had some incredible fights, many of which took place during Doctor Strange In the Multiverse of Madness. The events of WandaVision left Wanda looking for her kids in the multiverse. By channeling the power of the Darkhold, and attempting to kidnap America Chavez, the multiverse traveler, fans saw the darkest version of MCU Wanda.
In attempting to kidnap Chavez, Wanda performs some questionable actions on her former "friends" and by the end of the movie, she comes full circle, recognizing the error of her ways, making her an unhinged, yet morally questionable, the villain in this movie.
General Dreykov
Some of the best villains are the ones who use both intellect and force to achieve their goals. General Dreykov is one of those people. In Black Widow, General Dreykov is revealed to be the man who mind-controls his widow and the only way to break out of his control is through the red dust powder.
What makes General Dreykov so intimidating is that not only is he taking girls at a young age, and training them to be his assassins, but, on top of that, he is mind-controlling them. What's even more surprising is that he is enacting his malicious agenda from behind a work desk.
Kingpin
One of the most complex and villainous characters, who also happens to deliver some of the most memorable quotes in the MCU, is Kingpin, aka, Wilson Fisk. Wilson first appeared in the Netflix Daredevil series and then reappeared in the Hawkeye series to reprise his iconic role. Like in Daredevil, Kingpin remains to be the "behind-the-scenes" villain, not revealing himself to the fans until nearly the end of the series.
What makes Kingpin one of the best villains in phase 4 is that not only does he have the raw combined strength of about 20 men, but he can mentally manipulate people to make them do his dirty work. He only steps in during the final moments, just showing fans how thought-out of a character he is.
Ultron
A consciousness who had the potential for true evil in Avengers: Age of Ultron, turned truly deadly in the animated What If...? series. It is known to fans that Ultron was always a ruthless character and in the What If...? series, Ultron's true intentions for the human race were made very clear.
Ultron, in the series, receives Thanos-level powers which allow him to wipe out all of humanity and is only stopped by the group of heroes The Watcher put together. This makes this version of Ultron truly villainous as he had both no conscious and a drive to fulfill his agenda.
Kang/He Who Remains
Introduced to fans in the Loki show was Kang the Conquer, known to fans in this series as "He Who Remains." Kang operates in a realm known as The Void, which exists outside of space and time, and his goal was to create a timeline where only he ruled. Anyone on his timeline who strayed away from their given paths was brought to the Time Variance Authority (TVA), and either turned into workers against their will or pruned into The Void.
What makes Kang truly dangerous is that not only will he do anything to own his sacred timeline, but he has yet to complete his agenda in the MCU. The show left fans with an ambiguous ending, not knowing how or when this methodical villain would return, making him not only a villain to look forward to in the future, but one the future new Avengers should fear.