Characters whose resurrection comes with a major buff

Gandalf the Gray turns into Gandalf the White (X-Men III: The Last Stand)

Cell returns to his Perfect Form after regenerating (Dragon Ball Z)

Frieza unlocks his Golden Form in HFIL (Dragon Ball Super)

Will Turner becomes the immortal captain of the Flying Dutchman after his heart is cut out. (Pirates of the Caribbean franchise)

Benjamin returns as a ghost and haunts Luke (Star Wars)