Several Marvel Cinematic Universe villains are still out there somewhere, and there might not be a better time to bring them back than in Phase 7. The MCU had a bad habit in many movies of killing off great villains, eliminating strong names like Killmonger, Hela, and The Mandarin.
However, several other villains remain alive, and no less than Sam Rockwell has mentioned the chance that Justin Hammer could return and cause some problems in the future. In an interview on the Happy Sad Confused podcast with Josh Horowitz, he said he would return as Justin Hammer after his arrest in Iron Man 2. While Iron Man is dead, seeing Justin Hammer causing problems in the future for War Machine or Ironheart would be an interesting turn.
Throughout the MCU, big-name villains have died. However, there are many great villains still alive. Some of them are in prison, and others are in hiding. A few were banished, but that doesn't mean they are gone forever. With Secret Wars possibly shaking things up on Earth, the MCU Phase 7 could open up the return for several characters.
The Best MCU Villains Who Should Return
Justin Hammer
At the top of the list is Sam Rockwell's Justin Hammer, since he is the one who got people talking about big returns. Hammer manipulated the American government to trust him to create new Stark armor for the military, but then he betrayed them, selling himself to the highest bidder. Iron Man killed Whiplash, but Hammer was quietly arrested after things got out of control.
Hammer is likely in the Raft or a lesser-security prison since he isn't a Supervillain. However, he has the brains and the pull to get people to free him if he offers to help them. He is nowhere near Tony Stark's level of genius, but he is good enough to cause problems in the MCU.
Baron Zemo
Baron Zemo shocked the world when he became a fan-favorite villain in The Falcon and the Winter Soldier. Zemo was a massive disappointment in Captain America: Civil War, but he was reinvigorated in his follow-up appearance. He could provide some great moments if he returns in the MCU Phase 7.
The Baron Zemo dance scene was a viral meme, but it was more than that. He had an actual personality in the Disney+ series and finally showed why Zemo is a great character. Not having Zemo as part of the Thunderbolts* was disappointing, and bringing him in later for a New Avengers appearance, or reconnecting him with Sam Wilson, could be great fun.
The Vulture
Sony and Spider-Man have complicated things for the MCU. A good example came in Morbius, when the Vulture was transported to that Earth, which made no sense. At the end of Spider-Man: No Way Home, the villains were transported back to their own Earths, but Vulture is from the MCU Earth, so he shouldn't have been transported anywhere.
Michael Keaton was fantastic as Vulture, and since the villain is older in the comics, it doesn't matter how old Keaton gets; he could still take on the role. There were hopes to see Vulture and someone like Scorpion (whom he saw in prison in the Spider-Man: Homecoming post-credits scene) forming a Sinister Six. That still could happen, and Vulture should be part of it.
Baron Mordo
Baron Mordo returned in Doctor Strange in the Multiverse of Madness, but that was an alternate Earth version of the character. It seems extremely disappointing that one of Strange's best villains was only a supporting character in both of his movies and never had a chance to show how dangerous he could be. Baron Mordo is still alive in the MCU and deserves a second chance to make Strange's life a living hell.
High Evolutionary
While it wasn't completely obvious, High Evolutionary is still alive after the events of Guardians of the Galaxy Vol. 3. By the end of the film, he was one of the MCU's most hated villains, mostly because of how he treated Rocket Raccoon and his animal friends. Of all the MCU villains, he is the one that fans wanted dead.
That didn't happen. Drax the Destroyer saved High Evolutionary's life and carried him to safety. While the Guardians are mostly gone, the future of the MCU is said to explore the Cosmos, which is a perfect place to see High Evolutionary return. Who he could torment is anyone's guess, but seeing this villain return could cause problems for whoever crosses his path.
Sharon Carter
One MCU villain assured to return is a former hero turned bad guy from the Captain America universe. In the Captain America movies featuring Steve Rogers, Sharon Carter was his ally and one-time love interest. She is also the niece of his greatest love, Peggy Carter. However, in Falcon and the Winter Soldier's twist ending, Sharon was unveiled as the villain known as the Power Broker.
This means she is pulling the strings behind several bad guys' actions and will be back to cause problems. When she will return is unknown, but expect it to involve Sam Wilson or Bucky Barnes unless she becomes an enemy of the New Avengers.
