Iron Man: Armored Adventures S02E16 - Extremis

When S.H.I.E.L.D. Agent Mallen is fired by General Nick Fury, Mallen takes the super-serum "Extremis" and mutates into a powerful maniac bent on revenge. When Iron Man tries to fight Mallen, he ends up defeated and in critical health... and his only salvation would be a dose of the selfsame Extremis.