Avada Kedavra

You utter a word of power that can compel one creature you can see within range to die instantly. If the creature you choose has 200 hit points or fewer, it dies. otherwise The target must make a Constitution saving throw taking 12d12 necrotic damage on a failed save, or half as much damage on a successful one

only the greater restoration spell can heal the damage done by this spell and only the wish spell can resurrection a creature killed by this spell