Which mutant in "X-Men: The Last Stand" is a Class 5 mutant and can destroy the earth?

The almost unstoppable mutant in "X-Men: The Last Stand" is a Class 5 and the most powerful. She is Jean Grey/Phoenix and she can destroy the entire planet. She possesses potentially limitless telepathic and telekinetic powers. She was born with these powers. As Jean Grey, she is seen as a caring and nurturing figure. When she is the Phoenix, she has to deal with being an Omega-level mutant. She becomes the physical manifestation of a cosmic universal force, the Phoenix.

In "X-Men: The Last Stand", Phoenix is a former member of the X-Men. The X-Men learn that she has survived the flooding dam from the previous film. When the mutant team currently find her, Grey has given in completely to her aggressive alternate personality as the Phoenix. Her mutant powers rival and even excel those of Xavier. Her multiple personalities are described as something from "an Oedipal drama played out". The Phoenix is seen as "someone embodying a Greek goddess", while Jean Grey has kept her human character as grounded in Freudian behavior as a victim and a schizophrenic. To mark the change of Grey into the Phoenix, her physical image is presented in colors of red, gold and black.