20 Most Powerful X-Men Villains Of All Time
15. Krakoa, The Living Island
No man is an island, but some mutants are. Krakoa, the Living Island, was an early adversary for the second generation X-Men (the era that introduced Wolverine, Colossus, Kitty Pryde and the like) and its name is fairly literal. Krakoa is a sentient island, which isn't exactly easy to put up a fight against. It all gets a bit King Canute fighting the tide.
Somehow transformed from a regular atoll in the Pacific Ocean by nearby nuclear weapons test, the Island That Walks Like a Man somehow developed a hive mind and planned on using the X-Men as an energy source. Again, it's difficult to fight the very ground you walk on, so they had to toss Krakoa into space to defeat it.
Still technically a villain through most of its appearances, recently Krakoa got transplanted to the grounds of Wolverine's new Jean Grey School For The Gifted as a high-end security system that swallowed up any undesirables that happened along. Technically no longer an X-Men villain, but Krakoa remains just as powerful.