Avada Kedavra

The "Killing Curse" from the Harry Potter series of books by J.K Rowling. Avada Kedavra is one of the three Unforgivable Curses (the other two being the Cruciatus Curse and the Imperius Curse. Use of an Unforgivable Curse on a human being is punished by a life sentence to the wizarding prison Azkaban. Use of one of the Unforgivables is impossible without a considerable amount of power, and the desire to cause harm behind it. Until the need for malice became canon, it was a common means of killing Potterverse Mary Sues.

Avada Kedavra was the curse which the dark wizard Voldemort used to kill Lily and James Potter, and left their year old son Harry with a scar on his forehead shaped like a bolt of lightning.