Illyana Rasputina or Magik is the sister of Colossus, the X-Men member featured prominently in Fox's Deadpool movies. She can teleport through time and dimensions, and destroy anything magical.
Legion
Legion or David Haller is the estranged son of Charles Xavier. He possesses abilities like time travel, reality-warping, pyro-kinetic telepathy, and probability manipulation.
Professor X
The X-Men get their name for Professor Charles Xavier, the creator of the team. Logically, he possesses immense power. Xavier is regarded as the strongest telepath who ever lived.
Franklin Richards
Son of Fantastic Four co-founders Reed Richards and Sue Storm, he's an Omega mutant, the strongest category. His powers include telepathy, time travel, and energy manipulation.
Jean Grey
Jean Grey was one of the original members of the X-Men and combined with the Phoenix Force, she is the strongest Omega mutant on this list. She devoured a whole star and a planet once!