The Killing Curse. This is one of the three Unforgivable Curses and it causes instant death to the victim. When cast, the curse is indicated by a flash of green light and a rushing noise. There is no known counter-curse for Avada Kedavra; but, it can be thwarted or prevented by hitting it with another spell mid-flight, by dodging it, and by interrupting the caster. According to J.K. Rowling, 'Avada Kedavra' is an ancient Aramaic spell which is the original of 'abracadabra.' It means "let the thing be destroyed."