answer:The spell Harry used on Malfoy wasn’t a killing spell. It was a spell that caused big, gaping wounds, which Snap was able to magically heal. No one in the Harry Potter books was brought back to life from a killing spell. As far as I can remember, the only reference to someone being brought back to life was in the story about the Deathly Hallows. One of the brothers brought his wife back using the stone, but she wasn’t really back and was unhappy.