Superman/Batman

Kryptonite: the deadly remnants of Superman's home planet and the only substance that can kill him. Once the rarest stone on Earth, the galactic gem can now be found all over the planet, leaving the world's mightiest defender vulnerable to attack from almost anyone at any time. With the help of Batman, the Man of Steel intends to rid the world of his greatest weakness, once and for all. But when word of this quest gets out, some villains see it as their last opportunity for revenge, and Superman faces some of the most treacherous weapons ever created, including Magic Kryptonite and a Kryptonite Doomsday monster.