20 Most Powerful X-Men Villains Of All Time
14. The Phalanx
Not that the X-Men got it any easier after fighting the ground beneath their feet. It wasn't long after they dealt with Krakoa that they had to deal with death from above, as the evil alien race the Phalanx tried to invade the Earth, with only Marvel's mightiest mutants in their way. And even they struggled to knock back these powerful villains.
An off-shoo of another species called the Technarchy, the Phalanx are “techno-organic beings”, boasting no true form but constantly changing shape. Which makes them tricky buggers to kill, because they can just reform any parts that are destroyed, dodge most attacks, and make themselves immortal and indestructible.
The other main threat they pose is spreading their techno-organic virus further, which infects other living beings and turns them into metal, whilst the Phalanx absorb all their energy. That's how Cable got his gnarly metal arm. So they're a double-threat: difficult to kill, and might turn you into one of them. Robot space vampires, basically.