One of the most anticipated MCU sequels is Captain Marvel 2, directed by Candyman filmmaker Nia DaCosta and set to be released in 2022, with Brie Larson reprising the role of the titular hero. We're still short on most details for the film (aside from the film taking place in the present MCU), with some rumors stating that the film will function as a quasi-Avengers film à la Captain America: Civil War and feature most of the remaining heroes (led by Carol Danvers) uniting against a larger threat.
Whatever the storyline is, there's sure to be some kind of event that moves Carol's story forward, and a great villain is key to doing so. Thankfully, there's no shortage of villains that could give Captain Marvel a challenge, whether they've been seen before in the MCU or not.
10 Yon-Rogg
When we last saw Jude Law's Yon-Rogg, he had been beaten by Carol and sent back to Hala as a message to the Supreme Intelligence. While he could have been judged and executed, it would be interesting if he survived and showed up in the Captain Marvel sequel years later.
Maybe he could play a role similar to Hannibal Lecter's in The Silence of the Lambs, where he's either aware of or has orchestrated the events of the film from behind bars (if he's in a sort of Kree prison), taunting and/or trying to manipulate Carol again when she interrogates him for information. This dynamic could further the antagonistic relationship between the two of them, and seeing Law in the role again would be a treat.
9 Michael Korvac
Michael Korvac was a cyborg transported to the main Marvel Universe from an alternate reality by the Grandmaster, who attempted to download the knowledge of Galactus into his system, suddenly becoming one with the Power Cosmic. Now essentially a god, Korvac sought to remake the Earth as his own utopia, but was stopped by the Avengers and the original Guardians of the Galaxy, and has reoccurred several times since.
Since Galactus hasn't been introduced yet, the MCU's Korvac could take inspiration from the version seen on The Avengers: Earth's Mightiest Heroes, where he was a human abducted from Earth and experimented on by the Kree. Given Carol's own history with the Kree, she could have a personal stake in trying to help Korvac, only for him to lose control and turn against her in the process.
8 Genis-Vell
Genis-Vell is the son of the original Captain Marvel (Walter Lawson/Mar-Vell) and the third character to take over the Captain Marvel mantle in the comics. Despite starting out as a hero, he was later driven insane by his inability to control his Cosmic Awareness (or omniscient ability) and destroyed the multiverse at one point.
Genis-Vell could instead be the son of Annette Bening's Wendy Lawson/Mar-Vell who is manipulated by another villain into believing that Carol is responsible for his mother's death, only to realize the error of his ways and become a force for good.
7 Titannus
Just because the Skrulls we saw in the first Captain Marvel are good doesn't mean there aren't Skrulls who skew more evil. If the rumors that the sequel plans to adapt (or at least set the stage for) the comic storyline Secret Invasion are true, then we could meet a few Skrulls who don't see eye-to-eye with the ideals of Talos or Captain Marvel. One such Skrull could be Titannus.
Despite being unable to shapeshift, Titannus possesses enhanced stamina, strength, flight, and a healing factor as a result of being experimented on as part of the Super Skrull project. While he wouldn't be the main antagonist, he could serve as an enforcer for the actual villain.
6 The Brood
Marvel Studios now has access not just to the X-Men but also their collection of villains. These include the Brood, a sadistic race of aliens who reproduce by forcing their eggs into a host, who then becomes one with the hive mind that makes up the parasitic species.
They've crossed paths with Carol Danvers in the comics before and could make for extremely scary and violent antagonists for a sequel that focuses on Captain Marvel's adventures off-world. While they might have to be toned down somewhat from their comic book incarnations, they could still make effective villains if handled well, and director Nia DaCosta's experience working in the horror genre on Candyman would help in that regard.
5 Kl'rt
Another villainous Skrull who could make their debut here could be Kl’rt, better known as the Super Skrull. Along with Titannus he could serve as an enforcer for the actual villain, with his cruel and power-hungry attitude clashing with the ideals of the other more peaceful Skrulls.
And since the Fantastic Four are due to make their MCU debut in the near future, it would be smart to introduce Kl’rt in this film so he could menace Marvel’s First Family later on—once he gets some enhancements, of course.
4 Veranke
Without the Skrull Queen Veranke, there would be no Secret Invasion storyline. If this is the direction Marvel plans to head in with the Captain Marvel sequel, then bringing in Veranke as an antagonist would go a long way towards planting the seeds for that arc to take place.
She could be introduced as the leader of a different faction of Skrulls (which include Kl'rt and Titannus) who as a result of persecution by the Kree believe that the only way the species can survive is by infiltrating other planets and getting rid of their inhabitants so as to take their places. Veranke would in fact manipulate events within the film to show other surviving Skrulls that Earth's heroes and humans can be just as cruel as the Kree and that Earth should be claimed by their species.
3 Supreme Intelligence
Carol probably still has a bone to pick with the Kree's Supreme Intelligence, and it's unlikely that the artificial being has forgotten about "Vers" between the events of the first film and its sequel. If so, it would be great to have the Supreme Intelligence get its revenge on the cosmic heroine, and could mastermind a scheme that results in another Kree-Skrull War, with Carol at the center of it.
This scenario could see Carol pushed farther than she's been before, and the Supreme Intelligence could have fun playing mind games once again with the hero. And as a plus, there needs to be a scene where we see the Supreme Intelligence in its comic-accurate true form.
2 Rogue
While it might be too soon to introduce mutants into the MCU, having Rogue play some kind of role in a Captain Marvel sequel would be a great way to establish her presence and the existence of mutants in general. It would be cool to see the infamous Carol Danvers/Rogue moment play out onscreen, where the young mutant attacks Carol and permanently absorbs not just her powers but a good chunk of her psyche and memories as well.
Seeing Carol struggle to recover who she once was while also getting a look into how the sympathetic Rogue deals with having Carol's powers and psyche (as well as being a mutant) would be a fascinating dual story for a sequel to follow.
1 Mystique
As with Rogue, it might be too soon for any X-Men characters to make their MCU debut, but we can't resist the idea of seeing not only Rogue but her foster mother Mystique as the antagonists in the Captain Marvel sequel. Mystique could be one of the very first mutants to be discovered in this universe and is hunted by the government along with her "daughter", before crossing paths with Captain Marvel.
After Rogue absorbs Carol's powers and Carol comes after her for revenge, Mystique could manipulate the young mutant into thinking that Carol's actions are in line with the rest of humanity's views on mutants, pushing Rogue into eventually joining Mystique in the Brotherhood of Mutants. Seeing Mystique in this role would make the character much more in line with her personality from the comics as opposed to Jennifer Lawrence's portrayal from the Fox films.