The Marvel universe features a lot of great superhero teams and franchises but one of the most interesting is definitely the X-Men. Rather than showcase a series of accidental heroes and alien visitors, the X-Men focuses on "everyday" individuals who were given powers through genetic mutations. Many of these former humans lived terrible lives and have interesting and often tragic backstories thanks to their "afflictions."

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This is even more prominent in the villains seen throughout the X-Men series, with many of them rising to power and developing a deep-seated hatred for humanity after being abused, discarded, or misunderstood by society. X-Men has seen some incredible "bad guys" over the years but some of them are much more iconic than others. Here's a look at some of the most well-known villains to ever terrorize the X-Men franchise.

10 Sabertooth

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It's hard not to feel pretty sympathetic for Sabertooth, as he has one of the most tragic backstories in the X-Men universe. His mutation manifested at a young age, causing him to accidentally slay his own brother as the two argued over a piece of pie. It seems like a somewhat comical way to introduce the character but from there, Victor Creed's childhood spiraled, as his father locked him in a basement and would take to pulling his teeth out, lambasting his son as a demonic entity. It would take Sabertooth chewing off his own hand to escape, and his bloodlust would only grow as the years would pass.

Although he's seen his "wholesome moments," by and large Sabertooth is a menace and shares an intense rivalry with one of the most iconic X-Men to ever exist, Wolverine. Their intense battles over the years have solidified Sabertooth as one of the most known villains in the X-Men universe.

9 William Stryker

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There are few characters in the X-Men franchise with as much of a deep-rooted hatred for mutants as William Stryker. A bit of a religious fanatic, Stryker would grow increasingly more leery of mutants throughout the franchise, at one point believing them to be a ploy from Satan himself to "corrupt humans" before they were born. He begins to believe that mutants have been touched in some way by the evil entity and even goes as far as to slay his own son and wife after finding out that his child was born with a mutation.

His fanatical desire to eradicate all mutants turns him into a televangelist, one that constantly preaches his anti-mutant beliefs to the general public. His ultimate goals involve kidnapping Professor X and brainwashing him to use his mental power to destroy all mutants. He even goes as far as to try to execute Kitty Pride on television. It took the X-Men combining forces with Magneto just to stop the crazed "preacher" from carrying out his plans.

8 Deadpool

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Deadpool is notorious for being one of the best anti-heroes that the Marvel Universe has ever seen. The Merc with a Mouth is constantly breaking the 4th wall and has been featured in a wide array of crossover events thanks to his charming, albeit unhinged, personality. But comic creators have also imagined Deadpool as something far more sinister and in one particular release, he becomes one of the strongest, deadliest villains that the X-Men have ever faced.

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In fact, Wade Wilson lays waste to a number of the iconic mutants in Deadpool Kills the Marvel Universe Vol 1:3. Fans are used to seeing the foul-mouthed mercenary as a semi-heroic figure but this much darker take on the character proves that, if he wanted to, Deadpool could be one of the worst supervillains the Marvel universe has ever seen.

7 Dark Phoenix

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It's impossible to create a "best X-Men villains list" without including a nod to Dark Phoenix somewhere. Starting her comicbook life as Marvel Girl, Jean Grey has been an important and poignant part of the X-Men team ever since her inception back in 1963. She's well-known for her alias, Phoenix, as well as her telekinetic and telepathic powers. For the most part, Jean Grey has been seen as a loving, nurturing, and respected member of the team. She even married a well-known X-Men member, Cyclops.

But Jean Grey's journey took a variety of dark twists and turns with the Dark Phoenix saga, in which she was corrupted by the villain, Mastermind. She's regarded as one of the strongest and most imposing villains to ever grace the X-Men series.

6 Mastermind

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Speaking of Mastermind, his trademark form of mental manipulation has been plaguing the X-Men ever since his creation in 1964. There isn't a lot known about Jason Wyngarde's former life, but it is shown that he was a "carnival mentalist" for some time. Later in his life, he became a founding member of the Brotherhood of Evil Mutants and at one point became a prominent member in the ever-imposing Hellfire Club. It was there that he became a pivotal part in transforming Jean Grey into Dark Phoenix.

Mastermind has the ability to create intense psychological illusions, which he uses to help manipulate his foes. It's said that he can make others "see anything he wants them to see" and it's easy to understand why his mental prowess is enough to break even the strongest of heroes.

5 Onslaught

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In 1996, X-Men introduced one of the strongest and most imposing villains the franchise had ever seen with Onslaught. Through a long series of events, Onslaught eventually manifests thanks to the dark energies from the subconscious of Professor X and Magneto, birthing a villain that was capable of laying waste to some of the strongest heroes in the Marvel universe.

Possessing the abilities of Magneto, Franklin Richards, Nate Grey, and Professor X, Onslaught possesses Psychic Omnipotence, a near unlimited source of mental power. Its abilities include magnetic field manipulation, energy projection, telekinesis, telepathy, sensing mutants, and it is even capable of affecting and shaping reality itself. In one instance, Onslaught was strong enough to take on both the Avengers and Fantastic Four, simultaneously, and emerge victorious (for a time).

4 Nimrod

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The Sentinels are one of the most iconic enemy groups the X-Men face throughout the franchise. The iconic purple-painted armor-clad villains are so well-known to X-Men fans that they were even included as playable fighters in the Marvel Vs. Capcom series. But among these mutant-assassinating foes stands Nimrod, a unique Sentinel that possesses immense strength and fortitude.

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The character was first introduced in 1985 and is a creation of the Sentinels themselves, from an alternate future where the entities rule. He's capable of shapeshifting, interfacing with computers, projecting energy, and teleportation. What makes him truly imposing is his superhuman strength, nearly indestructible form, and his ability to regenerate. Nimrod has been featured throughout multiple storylines in the X-Men Universe and always proves to be a deadly foe.

3 Mr. Sinister

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Nathaniel Essex can be considered the polar opposite of William Stryker. He was once a scientist and becomes obsessed with the idea of transforming the human race into superpowered beings through evolution. Mutants become his main focus, as he believes unlocking their potential is the means towards creating the perfect species. His run-in and subsequent alignment with Apocalypse grant him increased presence, as the villain uses technology from the Celestials to turn the mutant-loving scientist into an ultra-powerful being.

After gaining powers and becoming Mr. Sinister, he only increases his attempts to craft the perfect human form. He even believes Cyclops and Jean Grey to be pivotal in manufacturing a human with the best possible DNA. His fanatical ideals and ruthless aggression towards his goals have caused him to have many conflicts with the X-Men over the years.

2 Apocalpyse

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Apocalypse has one of the richest stories in all of the X-Men universe, spanning thousands of years and developing the character as one of the most imposing threats that planet Earth has ever seen. Originally thought to be a "kind and caring man," Apocalypse would rise to become an influential villain capable of amassing armies and causing conflict wherever he went. Through loss and heartache, Apocalypse's powers would completely emerge, causing him to stop aging and giving him a slew of incredible abilities, all outlined by incredible strength and a genius-level intellect.

He would travel the Earth for thousands of years, convincing developing civilizations that he was a diety and using his powers to turn them against one another, inciting wars and conflict. He stands as one of the most well-known and feared supervillains in all of X-Men.

1 Magneto

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Although Apocalypse is definitely one of the strongest and deadliest villains to grace the X-Men series, it's hard to argue that Magneto is arguably the most iconic villain to ever exist in the franchise. Even fans who aren't well-versed in X-Men lore will recognize the metal-manipulating mutant. Once good friends with Professor X, Max Eisenhardt would grow into a seriously powerful supervillain who carries the belief that mutants are genetically superior to humans, and that they should be the ones to rule the planet.

He may not have a slew of powers like some of the other villains featured on his list, carrying mostly magnetic manipulation (which also allows him to fly by defying gravity through the use of magnetism) but Magneto is a truly ruthless foe that is incredibly tactical, calculated, and capable of doing some serious damage to both humans and heroes alike.

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