Avada Kedavra

Avada Kedavra — the Killing Curse — is the most terrible of the three Unforgivable Curses. Cast properly, it kills outright: a jet of green light, a sudden rushing sound, and the target falls dead with no visible mark on the body. There is no way to heal what it does, no shield charm that turns it aside, and no defense beyond getting out of its way or putting something solid in its path.

The incantation is believed to derive from the ancient Aramaic phrase Abhadda Kedhabhra — "let the thing be destroyed." That same root is the likely origin of the stage-magic incantation "abracadabra," which is sometimes used in the wizarding world as a deliberately watered-down joke. The curse itself is anything but funny. It requires not only the wand movement and the words but a deep, sustained, undivided desire to kill. As Bellatrix Lestrange once explained to Harry, dabbling in it without intent produces nothing — "you've got to mean it."

Lord Voldemort favored Avada Kedavra above all other spells. He cast it on Lily and James Potter on the night of October 31, 1981, killing both. When he turned the curse on the infant Harry, however, Lily's sacrificial protection turned the spell back on Voldemort himself — the only documented case in wizarding history of a person surviving a direct hit from the Killing Curse. The accidental consequence of that backfire would shape the entire course of the wars that followed.

Use of any of the three Unforgivable Curses on another human being is a class-A criminal offense under wizarding law, and a single confirmed use is enough to earn a life sentence in Azkaban. During the Second Wizarding War, the Ministry briefly authorized Aurors to use them in combat against Death Eaters — a decision still debated decades later as a moral failing of the war effort.