The most powerful mutant in these films, told from childhood to keep most of it locked away, by the man who was raising her.
Jean Grey is played by two actors across two runs of films, and both times the story is the same: her power is greater than the team’s, Charles Xavier decided when she was a child to wall part of it off, and he did not tell her. The Fox films tried this twice, in The Last Stand and again in Dark Phoenix, and neither attempt is loved.
What survives both attempts is the relationship with Logan, which the films handle better than the cosmic material. Famke Janssen and Hugh Jackman are the reason The Wolverine has anything to grieve about.