The X-Men are an organization built by Professor Charles Xavier to aid mutants all across the planet but that doesn't mean every single mutant on Earth has been a part of the superhero team. While some have taken up a path filled with goodness, some have joined hands with evil.

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There aren't many differences between mutants and superhumans, although the former regularly suffer from discrimination. This makes the job for the X-Men a bit tougher as they not only have to look for threats against the planet but also guard their own against the human race, who can turn on them at any given point. Despite being one of the strongest teams in the Marvel Universe, some of the most powerful mutants have not found a place in the X-Men.

10 Domino

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Domino is well-known for her exploits with the X-Force but quite surprisingly, she has never been a part of the X-Men, despite having every single skill in the book. She is smart, decisive, and has a skill-set that could be very valuable to the superhero group. It is not just about her luck, but also her ability to hold her own on the battlefield. Domino is one of the best hand-to-hand combatants in the mutant industry. She has gone on several Black Ops missions.

9 Justice

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There have been numerous mutants with telekinetic abilities and Justice is one of the strongest. His real name is Vance Astrovik and he has been a part of the New Warriors. Despite his telekinetic abilities not being as refined as one would expect it to be, Justice makes up for it with his leadership skills. He has led the New Warriors several times before going on to become a part of the Avengers. It would be lovely to see him join the X-Men for a bit as well and who knows, he might become their leader.

8 Quicksilver

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Quicksilver is one of the fastest Marvel superheroes of all time and despite starting out as an X-Men supervillain, Magneto's son eventually went on to become a member of the Avengers. He was also a part of the Brotherhood of Evil Mutants, but that's expected because his father was once the leader of the group.

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Quicksilver has always been close to the X-Men yet he has never shown any intention of fighting by their side. His superpowers are very useful, especially the ones he developed later on, like teleporting into the future. Charles would have loved to have him on his side.

7 Sunspot

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A mutant who has the ability to absorb solar energy, Sunspot is a very popular member of both the X-Force and the New Mutants. Despite training to become a part of the X-Men, Sunspot has never really joined the group officially. Hailing from Brazil, Sunspot is a likeable character who is friends with almost everyone he has worked with in his career. Hopefully he'll get a place in the X-Men very soon.

6 Manifold

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Manifold aka Eden Fesi is a very popular mutant and part of a group called the Secret Warriors. Although he has been a part of various mutant teams, he has never joined the X-Men as he has opted to remain with the Secret Warriors, instead. It was Nicky Fury who recruited Manifold after the mutant received some expert training in teleportation from Gateway. Living in isolation for most of his life, Manifold had to evolve in order to become a team player. His abilities are very useful for any superhero group.

5 Deadpool

Deadpool Sins of the Past

Deadpool has never been a part of the X-Men, despite being an important member of the X-Force and Cyclops' black-ops Z-Force. The Regenerating Degenerate could have taken the popularity of X-Men to a whole new level if he ever joined the group, but Wade Wilson has never really been a proper superhero. He is an anti-hero and a mercenary who'll do anything for the highest bidder. It's his ability to break fourth walls that has granted him such a huge fanbase.

4 Nate Grey

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Coming from an alternate reality in the Age of Apocalypse, Nate Grey is the son of Jean Grey and Scott Summers. Widely regarded as one of the strongest telepaths to ever grace the Marvel Comics, Nate is known as X-Man.

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From his name, it could be guessed that he has been a part of the X-Men but in reality, he has never become a full-fledged member of the mutant superhero team. He has aided them here and there but never has he become a part of the family.

3 Scarlet Witch

Scarlet Witch in Avengers Infinity War

Scarlet Witch might be one of the only superheroes with mutant origins to have caused more damage to their own species rather than the human race. The House of M storyline is still regarded as the worst thing to happen to mutants in the history of the Marvel Universe. Wanda Maximoff has long been part of the Avengers but she might never step into the world of the X-Men. A powerful sorceress by stature, Scarlet Witch's ability to alter reality is both deadly and useful.

2 Quentin Quire

Kid Omega posing for the camera

Going by the name of Kid Omega, Quentin Quire rebelled against the Charles Xavier school of thinking as he thought it was much better to simply become a murderer by letting his powers loose. Quentin is an unstable individual who can not only form ideas at a rapid rate but can also control other people's minds. The energy coming out of his body is something entirely unique. It allows him to exist without any physical form. This incredibly powerful mutant has never liked the X-Men and he never will.

1 Franklin Richards

Franklin Richards split image in Fantastic Four comics

Franklin Richards is an Omega-Level Mutant with reality-warping abilities. His superpowers are absolutely incredible. He can do anything he pleases including creating an entirely new universe or destroying one. The son of Invisible Woman and Mr. Fantastic, Franklin is still just a kid in the main continuity, but many future versions of him have already been shown. If he ever properly joins the X-Men, he will become their strongest member ever.

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