Beast

Born with unusually large hands & feet, strength as well as agility
Recruited by Professor Xavier, became a founding member of the X-Men
Drank a serum he created which further mutated him into a blue-furred creature
Used his new powers to stop a rival from stealing his work;
Didn’t take the antidote in time & remained permanently stuck in his new blue form
Founding member of X-Factor, later returned to Jean Grey School as vice principal
Underwent a Secondary Mutation, mutate further into a more feline creature