What is the Killing Curse?

The story behind the answer

Avada Kedavra is the Killing Curse—one of the three Unforgivable Curses. When cast, it causes instant, painless death with a flash of green light, and there is no counter-curse; typical shields can’t stop it. By contrast, Crucio tortures, Reducto blasts objects apart, and Sectumsempra slashes the target.

Feared for its finality, it’s Voldemort’s signature spell; Harry survives it only because of his mother’s sacrificial protection, which made it rebound. Memory tip: Avada Kedavra sounds like “a cadaver” and echoes “abracadabra”—but with deadly intent.