Thanos' days as the big bad villain in the Marvel Cinematic Universe are numbered. With the Guardians of the Galaxy and The Avengers teaming up for Avengers: Infinity War and the as-of-yet untitled Avengers 4he doesn't stand a chance, even with the all-powerful infinity gauntlet on his hand. He's been the imminent threat to our heroes ever since the end of Phase One with The Avengers mid-credits stinger.

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The plan even then was to build up the universe with Thanos' quest for the infinity stone so he could face off with the heroes of Earth in Infinity War, but what lies ahead for the MCU after he's inevitably defeated? What villains could possibly rival the cruel and mighty Thanos armed with control over time and reality itself? It's possible that we've already seen them subtly introduced on-screen for the future, as Marvel Studios likes to do with its foreshadowing, or they could bring a completely fresh face in to shatter the Avengers' world. Here are 15 Marvel villains we think should take Thanos's place as the big bad conqueror of the universe until The Avengers eventually put a stop to them over the course of the next few phases of the MCU.

15 ULTRON

Ultron

Didn't The Avengers already beat Ultron once? Technically, yes, but Ultron isn't exactly known for just laying down and dying after one beat-down. As an artificial intelligence, it would be catastrophically stupid not to save a backup of his programming somewhere in the world to take over if The Avengers stopped his plan in Avengers: Age of Ultron.

He was really just a few days old by the end of his first outing, so even with his rapid evolution, he could have grown to be so much more. With the additional time to evolve and grow, while he lays in wait to destroy the Avengers, he could become a truly menacing entity. Rather than cracking jokes, we could see an entirely different, humorless Ultron. One who's developed plans within plans, anticipating every eventuality, just like he does in the comics.

14 MODOK

The Marvel Comics villain M.O.D.O.K. strikes a threatening pose in Marvel vs. Capcom 3.

MODOK (Mental Organism Designed Only for Killing) is one of those villains that casual observers would think is completely ridiculous, but actual comic book fans knows that he's one of the most dangerous entities around. He may look like a giant floating angry head, but Marvel Studios made Ego, the Living Planet believable and threatening, so MODOK is far from off the table.

MODOK is super-intelligent thanks to the experimentation from AIM scientists that caused his mutation, which allows him to calculate potential probabilities with such extreme accuracy that it borders on precognition, so he could easily outplan the Avengers by predicting how they will react to every move he makes. He also has powerful psionic abilities that allow him to mentally control people, shoot energy beams and generate force fields.

13 DORMAMMU

Dormammu attacking Earth from the Dark Dimension

We briefly got to see the mighty Dormammu in Doctor Strange, and while Stephen Strange did manage to strike a bargain with him (eventually), there's no reason to believe that such an all-powerful being will stick to his word and not come back to threaten the Earth.

Just like Thanos, Dormammu was the bigger bad guy pulling the strings behind the scenes in Doctor Strangeusing Kaecilius as his Loki to set up the fall of the Earth. In the comics, Dormammu has faced off against Dr. Strange numerous times, always only being temporarily delayed rather than defeated. He's essentially an all-powerful god, so an Infinity Gauntlet is small potatoes to a guy like Dormammu, and a powerful sorcerer like Doctor Strange is nothing more than a minor hindrance.

12 MEPHISTO

mephisto-marvel

Though Mephisto is technically a Class Two Demon or Hell-lord, he often delights in impersonating the biblical Satan. He rules a fiery nether realm, which he refers to as Hell, and he is empowered by the souls of the damned often striking deceptive bargains with the living, so for all intents and purposes, Mephisto is essentially the Devil of the Marvel universe.

Mephisto would be a far more frightening big bad for the MCU, because not only would the threat of damnation and eternal suffering linger over each character's head, but also Mephisto is particularly adept at sowing discord among people, so he could divide the Avengers and the Guardians of the Galaxy, slowly corrupting them from within before unleashing the armies of Hell upon the world.

11 MORGAN LE FAY

morgan-le-fay

Marvel's Morgan le Fay is based on the powerful sorceress of Arthurian legend. She is granted immortality thanks to her Elven heritage, and she has used her long life to master the mystic arts. Aside from immortality, she has the ability to see into the future, possess human beings in her astral form and all other powers granted by her study of dark magic.

She has faced off against the Avengers numerous times and has been known to employ the monsters and weapons of Asgard in her pursuit of ultimate power. Even when her physical body is destroyed, her spirit has restored it, so she can essentially never be defeated. It would make for an interesting twist in future Avengers movies if they thought they had destroyed her, only for her to return at the most inopportune time.

10 THE  LEADER

leader

The Leader would be a great twist big bad for the MCU because we've actually already seen his origin story. Way back in 2008's The Incredible Hulk, after Dr. Samuel Sterns helps Emil Blonsky unleash his Abomination form, he's hit with some stray chemicals and his head starts to mutate and grow.

Like most of The Incredible Hulk, we never saw a hint of him ever again, but with the return of Thunderbolt Ross in Captain America: Civil War, we know that the movie is still canon, which means that The Leader is out there somewhere. He's an ultra-intelligent evil mastermind who could easily have been plotting in the background for the last nine years, moving pawns into place to enact his ultimate plan after Thanos falls. And with genius-level skills in genetic engineering, he could be amassing an army of mutant beasts right under our heroes' noses.

9 LIVING TRIBUNAL

The-Living-Tribunal

Some of these villains tend to usually be Earthbound, so it would be a stretch to bring the Guardians of the Galaxy into the fold for the final showdown. However, the Living Tribunal is a cosmic entity who has existed as long as the multiverse itself and acts as the highest judge of all existence. He has three faces that represent three separate personalities and the three aspects of every universe: Equity, Necessity and Vengeance.

The Living Tribunal is entirely impartial in his judgment, acting only in the greater interest of the universe. The Earth has occasionally been a danger to the rest of the universe, which brings the Living Tribunal around to erase it from existence until they can eliminate whatever threat summoned it. Rather than be a mastermind behind the phases, it could be the potential judge if the Avengers couldn't save Earth.

8 ENCHANTRESS

Enchantress the Asgardian magic user

Amora the Enchantress was born somewhere in Asgard to unknown parentage, and in adolescence ran away to study sorcery and the mystical arts, becoming one of the most powerful beings in the entire Marvel universe. She possesses all the traditional attributes of an Asgardian goddess, including incredible strength, speed and longevity with a nearly endless array of additional sorcerous abilities that outclass even Earth's Sorceror Supreme, Doctor Strange.

She has often been the mastermind behind plans to bring down the Avengers, enlisting the help of major villains, legendary monsters and entire armies. She could even surpass Thanos as the big bad, as she'd likely take a more active role in attacking the Avengers head-on from time to time, unlike Thanos who's basically sat on a throne for five years scheming.

7 BLACKHEART

Blackheart

Blackheart was created by Mephisto from the accumulated evil of the Earth to corrupt and destroy the people of Earth, and while being the "son" of Mephisto may make him sound less threatening at first, Blackheart eventually decided to rebel against his father and seek a more pure form of evil. This makes Blackheart an interesting potential major villain for the MCU because he could show up before, after, or in tandem with Mephisto for a showdown with ultimate evil.

Blackheart even apparently killed Mephisto at one point, banishing him from Hell and becoming even more powerful. He could also potentially be what links up Agents of S.H.I.E.L.D.the Netflix shows and the movies, because he's frequently clashed with the likes of Daredevil, Ghost Rider, Spider-Man and Doctor Strange, never fully being defeated, but rather continuing to corrupt the innocents of Earth.

6 MOLECULE MAN

Molecule Man in Marvel Comics

When working as a laboratory technician at a nuclear plant, Owen Reece accidentally activated an experimental particle generator, which blasted him with an unknown form of radiation that unleashed within him incredible psionic powers on a cosmic scale and made him one of the most powerful beings in the universe.

The Molecule Man has complete control over all matter down to the molecular level, as well as all energy, meaning that he can create, transform or vaporize anything he can imagine in his mind, and eventually alter reality on a multiversal scale. He often has more complex motivations than the typical villain as well, often seeking emotional fulfillment and human sympathy in his grand actions of god-like power, compared to Thanos' sort of single-minded quest to be the all-powerful ruler of reality.

5 TRYCO, CHAMPION OF THE UNIVERSE

Tryco-Champion-of-the-universe

Tryco Slatterus, Champion of the Universe, would be a logical next step as the multi-phase big boss in the MCU, with his only goal being to prove himself as the ultimate being in the universe, seeking to challenge and defeat the greatest warriors in the universe. He's an ancient Elder of the Universe and the only survivor of a long-dead race from a galaxy that was destroyed ages ago.

He has never been defeated, but he has been given enough of a battle to take his leave only to return later for a stronger champion. He was one of the holders of the Power Infinity Gem before Thanos was able to take it from him, but they have frequently worked together to wreak destruction on the universe, so he may already be involved in Thanos' plans.

4 BEYONDER

Beyonder Jim Cheung

Beyonder is a member of an ancient extradimensional race known as the Beyonders. He was dragged to Earth from his own dimension by a group attempting to use a tachyon beam to attract Vibranium meteorites. In Beyonder's unique perspective, every sentient being on Earth was inherently "incomplete." When he decided that the driving force of all sentient beings was desire, he summoned the greatest heroes and villains of Earth and the Cosmos for the Secret Wars (by writer Jim Shooter and pencilers Mike Zeck and Bob Layton).

During the classic storyline, Beyonder brought the greatest heroes and villains of the Marvel Universe together for a massive battle royale in an extra-dimensional spacetime location of the his creation called Battleworld. This is the natural next step from Avengers: Infinity War and would pit heroes against heroes and villains against villains.

3 RED SKULL

Red-Skull-Hugo-Weaving

A lot of Marvel fans were surprised when Red Skull was seemingly destroyed at the end of Captain America: The First Avenger, since he's one of the most dangerous and resilient enemies of the Avengers in the history of Marvel. However, there's been significant evidence to support a popular fan theory that he was merely teleported away by the cosmic cube, and is biding his time to return and vanquish Captain America.

It's possible that the Red Skull has even been working with Thanos, lending him the scope and power of HYDRA to manipulate events on Earth and find the remaining Infinity Stones. While Thanos and the Infinity Gauntlet seem larger-than-life and all-powerful, Red Skull has exhibited a lot more torture and pain on the Avengers and Earth over the years than Thanos ever has.

2 KANG THE CONQUEROR

Kang-Phase-4

Kang the Conqueror has been a thorn in the side of the Avengers since way back in issue #8 of the original volume of The Avengers by Stan Lee and Jack Kirby. Kang was originally Nathaniel Richards, a genius-level historian, physicist, engineer, technician and warrior from the 30th century who discovered Victor von Doom's time travel technology.

Kang has traveled all over space and time, manipulating history and the future to suit his whims. In addition to mastery over time and space travel, Kang is armed with the technologies, armor and weapons of the far distant future. He can't be outgunned and he has studied the history of the Avengers, so he knows their every move before they make it. Theoretically, Kang could go back in time to kill Steve Rogers before he became the super-soldier, or Tony Stark before he escaped the cave.

1 NAMOR THE  SUBMARINER

Namor

Prince Namor of Atlantis has literally been around since Marvel Comics itself, first appearing in Marvel Comics #1 by Carl Burgos published by Timely Comics. He has frequently fought as both a short-fused hero and a hostile invader seeking vengeance for the misdeeds of the surface-dwellers committed against Atlantis.

He's essentially invulnerable with a seemingly endless lifespan, genius-level intellect, incredible strength and powers derived from both his heritage as an Atlantean and a mutant half-human. He has the massive armies of Atlantis at his disposal, though he often seems cruel and ruthless, his motivation tends to come from the desire to protect his kingdom, so his motivations are complex and sympathetic, but he could still pose a genuine threat to every surface-dwelling being on Earth, providing a good answer to Marvel's "villain problem."