The X-Men are one of the most formidable teams in the Marvel Universe, boasting some of the most powerful mutants on the planet. Their mandate is to not only protect a world that hates and fears them but also to find young mutants and train to use their powers. In their missions, they face the double-edged sword of racist humans with their mutant-destroying technology and mutant supremacists trying to destroy the human race.
The X-Men have faced down some powerful foes over the years and have always come through thanks to a combination of skill, power, and great leadership. However, sometimes, there are some villains that they shouldn't technically win against but do anyway.
10 SHOULD BE ABLE TO BEAT THE X-MEN: The Sentinels
The Sentinels are humanity's reaction to mutantkind. These deadly machines' entire purpose is mutant extermination and they have all the tools for the job, especially as the years have gone by and the designs have progressed in power and efficiency. Armed to the teeth, they are the ultimate expression of humanity's hatred.
With many different designs over the years, ranging from the classic giant killing machine to smaller man-sized models to highly adaptable wild ones, the Sentinels have all of the weapons they need to destroy the X-Men but haven't.
9 WHY THEY CAN'T: Humanity Is Dumb
The Sentinels should easily be able to destroy the X-Men-- they've been fighting the team for years now and have records on the way their powers work, their tactics, and so on. Their computer systems and the growing technology that fuels them should have allowed them to take out the team ages ago but the main thing that stops that from happening is that the humans never send them out in great enough numbers.
If enough Sentinel were sent out, the X-Men would have no chance. The numbers games would get to them-- they might be able to take out some of the Sentinels but little by little, they'd lose more and more members until none were left. The only reason they were never sent out in such overwhelming numbers has to because the humans are dumb enough to think a few will do the job.
8 SHOULD BE ABLE TO BEAT THE X-MEN: The Shadow King
The Shadow King is one of the most powerful telepaths in the world. Striking from the Astral Plane, he hasn't had a physical body of his own in a long time, preferring to possess others with his vast mental powers. His goals are simple-- take complete control of the world and rule it as the overseer of all living things.
While he's not the most powerful telepath on Earth, his powers and skills are quite formidable and have made him a danger to the X-Men every time they face him. While they've always survived his attacks, it's only by the skin of their teeth.
7 WHY HE CAN'T: His Plans Aren't Well Thought Out
The Shadow King has been facing down both Xavier and the X-Men for a long time and by now, he should have learned something about fighting them. His problem is that he doesn't take advantage of his possession abilities-- he usually tries to take out the telepath first, which never works out very well.
If he was a better planner, he'd possess someone like Wolverine and have him start killing the telepaths in their sleep. Without the telepaths, the rest of the team would find it impossible to resist the Shadow King or counter his powers, making them easy picking for him. Fortunately for them, Shadow King isn't very smart.
6 SHOULD BE ABLE TO BEAT THE X-MEN: Mister Sinister
Mister Sinister likes to stay in the shadows, so much so that it's easy to forget just how dangerous he is. A master geneticist, Sinister knows more about mutants and how they work than anyone on the planet and is always looking for more mutants to experiment on, both to gain a better understanding of mutants and to create more powerful servants to use against his foes.
Sinister has been responsible for some terrible atrocities in his time and the X-Men have always been able to stop him but in reality, there's really no reason why they should be able to-- he knows how to take away mutant's powers and his own wide repertoire of powers make him a powerful threat even without all the servants.
5 WHY HE CAN'T: His Obsession With Genetics
Mister Sinister's knowledge of mutant physiology should allow him to easily defeat the X-Men. He could create a virus or something that would counteract the powers of the X-Men, leaving them powerless and easy to take on. It's recently been revealed that he had a gene bank with every mutant's genes in it and cloning technology, meaning he could throw endless armies of clone mutants at them.
He doesn't because of his obsessions with genetics and watching how certain X-Men's genes interact with each other, like Cyclops's and Jean Grey's. He's spared the X-Men his full attention because of this. With his powers and resources, he should be able to defeat them easily but he chooses not to because of his obsession with science.
4 SHOULD BE ABLE TO BEAT THE X-MEN: Apocalypse
Apocalypse has been around for thousands of years and is one of the most powerful mutants to ever exist. Obsessed with survival of the fittest, Apocalypse has used his powers to attack the X-Men and the world at large for years, sometimes with help from his Horsemen. Outfitted with Celestial technology and armor and thousands of years of experience, he's even proven more than a match for a pre-Mjolnir Thor.
One of the most powerful villains the X-Men have ever faced, there are entire alternate worlds and futures ruled by Apocalypse but for some reason, the X-Men are always able to defeat him.
3 WHY HE CAN'T: Hubris
Apocalypse believes in survival of the fittest and he believes that he is the fittest. While one can make the argument that he is, technically, one of the fittest mutants around, his belief in his greatness has held him back. He makes stupid mistakes most of the time because he assumes that he's so much better than everyone else.
This is a huge mistake, especially since over the years, the X-Men have defeated him in just about every encounter. For some reason, he still believes that he is better than them even though he can never defeat them. It makes little to no sense and can only be chalked up to his own gargantuan hubris.
2 SHOULD BE ABLE TO BEAT THE X-MEN: Magneto
Magneto is one of the most powerful mutants on the face of the planet. His mastery of magnetism means that the modern world is pretty screwed if he really gets serious- he can tear apart anything made of ferrous metals and generate electromagnetic pulses that can easily burn out electronics whenever he feels like it. He can control the iron in people's bloodstreams.
On top of that, he also has a helmet which renders him invulnerable to telepathic attack. He can raise powerful magnetic shields to protect himself from any assault. Magneto should be able to pretty handily defeat just about foe he comes across, not just the X-Men.
1 WHY HE CAN'T: His Belief System & Desire To Be Right
Magneto believes in the supremacy of mutants and, if he can help it, doesn't want to kill them. Far from it, in fact-- he wants to lead them against the humans. For this reason, he's always gone at the X-Men with kid gloves. He can kill any one of them whenever he wants, but he doesn't because he doesn't want to slaughter mutants.
He also wants them to realize that he was right and Professor X was wrong. He wants them to come to him willingly. He wants the fighting to end among mutants, and he wants to be the leader of their race.