Remember when the biggest complaint about the Marvel Cinematic Universe was its "villain problem" - that the antagonists of the films were underdeveloped characters that often perished by the time the credits began to roll?
Well, Kevin Feige. and co. have definitely addressed that issue over the years, delivering charismatic and complicated supervillains like
Killmonger, Thanos
and the Ravagers. In fact, there are quite a large number of villains currently still alive in the MCU with a few roaming free to whip up mischief however they see fit.
If Marvel Studios decides to move towards a
Masters of Evil saga after Thanos, there are plenty of members that could fill out its roster. And with Steve Rogers retired, Iron Man, Vision and Black Widow deceased, Thor and Captain Marvel off-world, and Hulk permanently injured, Earth's Mightiest Heroes might be more vulnerable than ever before.
The Real Mandarin
As we recently had reaffirmed, Marvel Studios President Kevin Feige has stated that the studio has plans to introduce the Real Mandarin in a future MCU project. This was first hinted at in the All Hall The King One-Shot but was never touched upon again in any of the films that followed Iron Man 3. Many fans think that the studio will use the upcoming Shang-Chi film to introduce the Iron Man foe now that Robert Downey Jr. has presumably filmed his last scene as Tony Stark.
Loki
After dying in Avengers: Infinity War, a "Hulk Smash" of a clandestine Tony Stark allowed Loki to escape with the Tesseract/Space Stone, creating an alternate timeline. It's presumed that the events of this alternate timeline will be recounted in the upcoming Disney+ Loki series but nothing has been confirmed by Marvel. Hopefully, Marvel attends SDCC this year after skipping the convention in 2018. At that time, Feige stated that Marvel would be attending in 2019 but D23 is also slated for this year, which in the past, has resulted in Marvel skipping SDCC.
Red Skull
With the Soul Stone taken from Vormir, the Red Skull is presumably out of a job. Does he return to Earth, perish from old age or set out to conquer some alien planet? While having somewhat of a benevolent nature while explaining the necessary sacrifice to acquire the Soul Stone, it's hard to imagine Johann Schmidt completely dropping his quest for power. He appears to have acquired some mystical abilities as well, as audiences saw him hovering off the ground while greeting Thanos and Gamora.
Prowler
As evidenced in the Spider-Man: Into the SpiderVerse animated film, the Prowler is Miles Morales' uncle who's depicted as thief and mercenary in the comics. One-time Miles Morales hopeful Donald Glover had a quick cameo as Davis in Homecoming that could potentially lead to bigger things down the road. Someone like Michael Chernus' Tinkerer (who's still at large) could create a power suit for Davis fairly easily.
Ghost
While not an outright villain, Ant-Man and the Wasp revealed that Ghost is capable of committing some pretty heinous acts when she becomes desperate. While Janet van Dyne stabilized the Quantum Energy threatening to destroy her, it didn't totally cure her. Now in hiding with Bill Foster, all it would take is for her to return to her villainous ways would be another desperate situation.
Abomination
The Incredible Hulk is something of a bastard step-child of the MCU thanks to complicated filming rights with Univeral Pictures, and the fact that Ed Norton was replaced with Mark Ruffalo. Still, that hasn't stopped William Hurt's Thaddeus Thunderbolt Ross from appearing in a number of subsequent films so it theoretically should be just as easy to bring back Blonsky. Kevin Feige and co. have also demonstrated that they have no qualms about switching an actor playing a costume or VFX-heavy character, with a new actor portraying Red Skull in Infinity War.
Mordo
The events of Doctor Strange illustrated that the sorcerers of the MCU have some unique and interesting abilities that only another sorcerer can really combat. To that end, the film's closing act saw a villainous switch by Chiwetel Ejiofor's Karl Mordo that probably makes him the most dangerous villain currently roaming the Earth. After he finishes targeting inappropriate magic users, who's to say that he won't decide to bring order to the rest of the world?
Justin Hammer
While not physically a threat, Justin Hammer's wealth makes him a credible threat to the forces of good. With Tony Stark no longer in the picture, it will be interesting to see what effect that has on Hammer. Perhaps he'll take that opportunity to grab the spotlight and sponsor his own superhero team - it would be a treat to see Rockwell's Hammer occupying the role that Norman Osborn played in the Dark Avengers storyline from the comics.
Helmut Zemo
Another non-physical threat, it's Zemo's mind that makes him incredibly dangerous. He's one of the few MCU villains to actually achieve their goal. However, his victory in splitting up The Avengers appears to be undone after Endgame which may prompt him to break free and begin anew. A collection of villains with Zemo as their master strategist would be incredibly dangerous to the current Avengers team that's operating without Iron Man, Steve Rogers, Vision, Black Widow, and an off-world Thor and Captain Marvel.
The Leader
Like the Abomination, Tim Nelson's Samuel Sterns, aka the Leader, hasn't appeared in another Marvel film despite the fact that The Incredible Hulk planted several seeds for a sequel. The prelude comic book for The Avengers revealed that Black Widow arrived in the aftermath of the Hulk and Abomination's Harlem throwdown and placed Samuel Sterns in S.H.I.E.L.D. custody. After the event's of The Winter Soldier and the disbanding of S.H.I.E.L.D., it's unclear whose custody Abomination and Sterns are in, though Thunderbolt Ross is a likely bet.
The Tinkerer
While having a minor role in Spider-Man: Homecoming, the Tinkerer's appearance might prove to be the film's biggest contribution to the future development of the MCU. In the comic's the Tinkerer is responsible for creating and upgrading a number of villain costumes and weaponry, including the Scorpion, Spider-Slayer robots, and Green Goblin. He would be a great addition to any super-villain team and would help non-powered villains like Justin Hammer and Zemo become a little more formidable.
Shocker
Bokeen Woodbine portrayed Herman Schultz, aka the Shocker, in Spider-Man: Homecoming and wielded a modified version of Crossbone's Age of Ultron gauntlets, thanks to the Tinkerer. Tom Holland's Spider-Man left Schultz webbed up before going after the Vulture but it's unclear whether he was captured by the police. Like Toomes, he's one of the few villains that knows that Peter Parker is Spider-Man.
Scorpion
Though only briefly appearing in Spider-Man: Homecoming, it appears very clear that Marvel is planting seeds to introduce the Sinister Six in a future Spider-Man sequel. Michael Mando portrayed the Marc Gargan version of the character in Homecoming, where it was revealed that he and Donald Glover's Aaron Davis (aka Prowler) were former partners. As witnessed in Homecoming final scene with Michael Keaton's Adrian Toomes meeting Gargan in prison, the latter definitely wants to settle the score with Spidey. With Far From Home adding Mysterio and the Chameleon, there's already enough Spidey Rogues to form the Sinister Six (Mysterio, Chameleon, Shocker, Vulture, Tinkerer, Prowler, Scorpion) though their usual leader, Doctor Octopus, has yet to make his debut.
The Vulture
Michael Keaton's Adrian Toomes had a change of heart about Tom Holland's Spider-Man after he saved his life and his daughter's, opting to play coy when asked to reveal the web-crawler's secret identity. Yet, Marvel and Sony appear to be building up to the Sinister Six, which in the comics, has a track record of being betrayed by at least one member who's attempting to reform or owes Spider-Man a favor. Keaton's Toomes could easily play such a part.
Ayesha/ The Sovereign
The Sovereign have a big bone to pick with Star-Lord and the rest of the Guardians of the Galaxy as Rocket Raccoon's theft of the Anulax Batteries and the Sovereign's subsequent retaliation brought great destruction to a race that deems itself superior to all others. As the closing moments of the film revealed, Adam Warlock will soon be targeting the Guardians but based on his comic book past, he'll likely end up joining their crew.