Marvel Comics boasts an unbelievably huge catalog of characters. With Disney's purchase of 20th Century Fox and their temporary rights to a number of Sony's Spider-Man characters, Marvel Studios now has nearly just as many characters at their disposal. 22 movies and hundreds of characters later, it may seem as if there's little room for even more powerful beings.
Could they introduce someone more powerful than Thanos? Definitely. The Mad Titan, Dormammu, and Ego are maybe the only truly powerful cosmic beings we've seen on the big screen, but there are many, many others who stand above these villains. It's difficult to determine who are the strongest ones, seeing as a number of cosmic entities constantly beat each other in the comics. But here is our take on the 10 most powerful Marvel cosmic characters not yet in the MCU, in no particular order.
Eternity and Infinity are two different beings, but they are essentially two sides of the same coin. One cannot live without the other. In practical terms, Infinity is Eternity's sister, but it's hard to speak about practicality when these two are officially described in the comics as being "Abstract Entities." Along with Death and Oblivion (more on them later), they represent the Cosmic Compass.
Both of them together are the personification of reality and represent the fabric of space and time. They have made a few non-abstract appearances, though. Once, Eternity actually spoke directly to Doctor Strange and helped him defeat Dormammu. Another time, Eternity met Hank Pym and thanked him for defeating the evil creature Chthon before granting him the title of "Scientist Supreme."
9 The Living Tribunal
The Living Tribunal is the right-hand man to the only being more powerful than him in the Marvel universe, the One-Above-All (more on him later). He is basically not the universe's, but the multiverse's judge, jury, and executioner. With everything that happens in the multiverse, from super-hero civil wars to giant planet-destroying battles, the Living Tribunal has the ability to instantly put an end to it, if he were so inclined.
He does not make many appearances because it is his duty to balance the multiverse, not stop everything bad from happening. He only intervenes under extreme circumstances. He's not quite Marvel's God, as he can theoretically be defeated (as has happened), but he is the closest thing to that.
8 Molecule Man
This is a tricky character to understand. The Molecule Man isn't exactly a person. Although he is represented by the human, Owen Reece, the Molecule Man was a force created by the Beyonders (yes, related to the previous entry), capable of destroying the multiverse. He has the ability to bend reality to his will. For MCU fans, he is essentially the embodiment of the Reality Stone.
He can create and destroy entire worlds. At one time, he even made Galactus nervous, to the point where the Devourer of Worlds actually obeyed Molecule Man's order to sit down. During this encounter, Galactus kept nervously remembering that the one in front of him could end him with a single thought. Now that's a force to be reckoned with.
Oblivion is another Abstract Entity that represents...well...oblivion itself. As in non-existence and the inevitable end of all things. He, along with Eternity, Infinity, and Death, came into existence together when the universe was created. While similar to Death, they're not as connected as Eternity and Infinity are to each other. Oblivion has a very strong rivalry with Infinity—so strong that they have ended up fighting each other on more than one occasion.
The Abstract Entities have the ability to use other creatures as avatars to act for them. During a particularly heated battle, Oblivion took on the form of the evil Inhuman, Maelstrom, while Infinity used the ex-Avenger, Quasar, to her advantage. Maelstrom attempted to destroy the universe as we know it but was fortunately stopped in his tracks.
6 The Beyonder
The Beyonder was once one of the most powerful beings in existence, on par with the Living Tribunal. He has since been retconned multiple times and, although he is still one of Marvel's strongest characters, he is not the cosmic force he used to be. Before his retcon, the Beyonder was basically the God of his own multiverse. He was shocked to discover the existence of Earth, similar to the man who first discovered new, tiny life-forms when looking under a microscope.
One of Marvel Comics' most well-beloved events is Secret Wars. The plot revolved around the Beyonder's desire to conduct an experiment with Earth's impressively powerful creatures, i.e, superheroes. He transported a large number of heroes and villains to a planet he created, named Battleworld, where (you guessed it) they all battled each other. Here's hoping the Beyonder and Secret Wars comes to movie theatres.
Out of everyone on this list, there is no doubt Galactus is the most well-known character. Ever since the Disney-Fox acquisition was teased, fans have been clamoring for the Devourer of Worlds to be Thanos' replacement in the next MCU saga. Galactus actually existed before the Big Bang. As an inhabitant of the planet Taa, Galan was from another universe.
When that universe collapsed, it formed a new universe. Ours. He was the only one to survive his universe's destruction and our universe's creation, where he was reborn as the mighty Galactus. He scours the universe with his heralds scouting out planets for him to consume. Galactus is not evil—he just has an insatiable hunger that can never be satisfied.
Death (or Mistress Death) is the most well-known member of the Cosmic Compass. She is probably the easiest to understand, as she can be compared to other mythological representations of death, like Hades and the Grim Reaper. According to the comics, she embodies decay and destruction. However, the most interesting aspect about her is her love life. One of the most famous comic book stories of all time has this as its main theme.
In Infinity Gauntlet, Thanos wipes out half the universe with the Infinity Gauntlet—not to balance the universe, but simply to make Death fall in love with him. Apart from Thanos, the one other being who is also madly in love with Mistress Death is Deadpool. On one occasion, the Mad Titan even cursed Wade Wilson with immortality, just so he could never be together with Death.
3 Phoenix Force
The Phoenix Force is said to also be an Abstract Entity, although not part of the Cosmic Compass. It possesses many ultra-powerful abilities. One is the ability to absorb and control any form of energy in the universe. It can also suck the life-force out of someone to the point of instantly killing, resurrect dead creatures, is nigh-omnipotent, and is immortal. These are just some of the Phoenix's capabilities.
It has a history of bonding to several subjects in an attempt to unleash its full power. Jean Grey has been mentioned many times as being the "One True Phoenix," which is why she is so destructive when possessed by the Phoenix Force. This was to an extent where she could destroy entire worlds. Audiences might be sick of the Phoenix Force after this year's X-Men movie, Dark Phoenix, but there is always the possibility of a future reincarnation in the MCU.
2 Lord Chaos and Master Order
As one can imagine, these two are in a similar abstract position on the Cosmic Compass, although at a lower level. Lord Chaos and Master Order are responsible for keeping the balance, having been referenced to as the "agents of universal balance," with each (obviously) representing chaos and order, respectively. Like Infinity and Eternity, they cannot exist without each other. This is the Marvel universe, though, so there is always some sort of physical encounter beyond their abstract nature.
Their most outrageous act happened due to Galactus's transformation from the Devourer of Worlds to the Lifebringer. As the Lifebringer, Galactus started restoring planets he had consumed to their original form. Chaos and Order determined that this shook the universal balance, and so brought him to stand before the Living Tribunal. The Tribunal, however, let him go, and so the agents of balance murdered the Living Tribunal (who was then brought back to life).
There really is no need to write anything to describe this being because he is Marvel's representation of God. He created any and all universes and has the ability to change anything to his will. He is omnipotent, omnipresent, and omniscient. Only once has he directly talked to living creatures. When an alternate universe Adam Warlock accidentally destroyed all of reality, he and Thanos were granted an audience with the One-Above-All.
He agreed to restore everything back to normal, as long as Warlock became the new Living Tribunal. As is clearly evident, the One-Above-All only acts if faced with a very, very extreme situation. Usually, the multiverse is left to thrive on its own. Under exceptional circumstances, the Living Tribunal may intervene. Only if, for example, the Living Tribunal is dead, and all of reality is gone (*cough*) does the One-Above-All step forward.