Marvel’s X-Men are easily one of the largest superteams in all of comics. With virtually every mutant in the Marvel universe having served on the team at some point, it makes sense that they would have quite the expansive roster.
Looking at both the past, present and future, the X-Men have come to house some of the most powerful and dangerous beings ever imagined. However, at times, even long time enemies have become allies and joined the distinguished team of heroes. To highlight some of the more dangerous characters to switch sides and join the team, here is our list of the 10 most dangerous X-Men villains who became members of the team.
10 Sabretooth
Though he may not always seem like it, Sabretooth has proven to be one of the deadlier X-Men villains from over the years. With powers very similar to that of Wolverine’s, Sabretooth is arguably far deadlier than Logan himself.
With a much more animalistic personality and pension for violence, Sabretooth has caused all sorts of problems for the team of mutants over the years, making it rather surprising when he actually joined the team. Likewise, though he is far from the most powerful mutant ever, his healing factor definitely makes him one of the more dangerous villains around.
9 Dr. Nemesis
As a villain, Dr. Nemesis was actually known as Dr. Death and caused quite a lot of trouble for the X-Men in the past. Upon joining the team, however, he then changed his name to Dr. Nemesis, and actually accomplished a lot of good alongside Beast.
As a man of science, Dr. Nemesis’ intellect proved to be invaluable for the team, assisting them with all sorts of missions. Likewise, since his mutant ability enhances his overall intelligence, it is easy to see why Dr. Death was also so dangerous to the team. Though he may not seem like a super-powerful threat, his brain has beaten brawn on many occasions, making Dr. Nemesis a very dangerous addition to the X-Men at the time.
8 Danger
For years, the X-Men’s Danger Room has allowed them to play out all sorts of scenarios, helping the team to improve their strategy and fighting abilities. However, at one point, it was actually revealed that another mutant helped make the Danger Room everything it was, and that it had been trapped there for years.
By the time Danger became strong enough to break free, she initially fought against the team she believed to have imprisoned her for so much time. Eventually though, Danger came around to forgive them and has been a pretty valuable addition to the team since. Though she isn’t the most popular mutant to ever serve on the team, Danger is definitely worthy of her namesake, especially after years of studying the movements of the most skilled members of the X-Men.
7 Namor
As one of the oldest mutants on this list, Namor is also one of the most complex. On one hand, he has a duty to his people as the ruler of Atlantis. On the other, his responsibilities there have often led him into conflict with other heroes of the Marvel universe.
On several occasions, Namor has been the villain of the story, thanks to disagreements and all sorts of other politics within the Marvel universe. Not only has he faced off against some of the Avengers, but he has also stood against the X-Men from time to time as well. Fortunately, Namor’s mutant DNA and political standing have also made him a valuable addition to the X-Men, giving them all sorts of advantages whenever he is around. Having proven just how deadly he can be at times, it is easy to see why Namor lands among the others on this list.
6 Quentin Quire
With a bad attitude and incredible power at his side, Quentin Quire made for quite the formidable foe over the years. Thankfully though, he eventually came around to join the X-Men, and has since offered a lot to the various teams in terms of both raw power and character development.
As one of the more powerful telepaths to ever hold a spot on the team, Quentin has actually helped the X-Men on quite a few occasions. While his personality can make him difficult to work with at times, the young man’s abilities have been shown to rival those of Jean Grey’s. Knowing this, it only makes sense that Quentin would be an incredibly dangerous character, whether he is with the X-Men or against them.
5 Emma Frost
It is no secret that Emma Frost is also one of the more powerful telepaths within the Marvel universe. Likewise, with the additional ability to turn her skin to diamonds, The White Queen is even deadlier than others may give her credit for.
For years, Emma has had a complicated relationship with the team, holding a more permanent role especially as her relationship with Cyclops got more serious. Regardless, Emma has always been a more ruthless member of the X-Men, and definitely isn’t afraid to cross certain lines when she needs to. Between her past and present actions alone, Emma has proven time and again exactly how dangerous she can really be.
4 Rogue
Due to the unique nature of Rogue’s abilities, she has the potential to rank much higher or lower on this list. However, considering how the character has been a major part of the X-Men for so many years now, it is easy to forget that she was originally introduced as a villain.
Thankfully, Rogue eventually came around to see things in a much more positive light, and has even ascended to some leadership roles within the various teams over the years. Fortunately, even if her current powerset is weaker than others have been, Rogue is still quite a deadly individual, making her a valuable addition to the team at almost any given point.
3 Scarlet Witch
Considering how Scarlet Witch has the ability to alter reality itself, it only makes sense that she ranks a bit higher than others on this list. For years, Wanda Maximoff has seemed to only grow more powerful as well, making her a terrifying friend or foe to both the X-Men and the Avengers.
Given that she once rewrote the entire Marvel universe, it is safe to say that Scarlet Witch can be pretty dangerous. With so much power at her disposal, Scarlet Witch can easily make for one of the Marvel universe’s greatest heroes, as well as one of its greatest villains.
2 Magneto
Magneto will always be one of the worst villains the X-Men have ever fought against. As an Omega-Level mutant, the character has devised all sorts of extreme and devastating plots, only to be thwarted by the X-Men in the end (on most occasions).
However, at times, he has also proven to be one of the team's most powerful members. Over the years, Magneto has joined/left/betrayed/saved the X-Men more times than one can count, making him one of the more complex characters that Marvel has to offer. Driven by the desire to save his people, Magneto’s alignment is really determined by what he believes the better option for mutantkind to be. On top of his incredibly powerful abilities, it is easy to see why Magneto can be frighteningly dangerous.
1 Apocalypse
Recently, Apocalypse himself has joined one of the many current teams of X-Men following Jonathan Hickman’s massive relaunch of the characters. Proving to be one of the evilest and ruthless villains the X-Men have ever faced, it is really surprising to see a character like Apocalypse fighting alongside them.
Of course, the villain does have ulterior motives at play, but that doesn’t change the fact that he is still a member of the team. Furthermore, considering the things he has accomplished in the past as well as his own mutant abilities, Apocalypse is arguably the most dangerous X-Men villain to ever switch sides and join the team.