Killing Curse

"Avada Kedavra's a curse that needs a powerful bit of magic behind it - you could all get your wands out and point them at me and say the words, and I doubt I'd get so much as a nosebleed."

- Barty Crouch, Jr. as Alastor Moody

.

Avada Kedavra (Av-ada Ked-av-ra) is the incantation name for the Killing Curse, one of the three Unforgivable Curses in the Harry Potter book and film series. The curse is mentioned in the first novel, but not actually seen until the fourth Harry Potter novel when Barty Crouch Jr. (disguised as Alastor Moody) peformed it in a classroom at Hogwarts on a spider.

Appearance and Effect
[[Image:Photo_49.jpg|right|thumb|200px|[[Bellatrix Lestrange]] using Avada Kedavra on Sirius Black] in the film adaption of Harry Potter and the Order of the Phoenix The Killing Curse is described as a jet of blinding green light, which, when it comes in contact with the target, results in the target's instant and painless death. Voldemort is known to have used the Killing Curse frequently. There is no known counter-curse for the spell; the only known defense against it are dodging the spell, hiding behind a physical barrier (which is destroyed upon impact), creating Horcruxes, and the voluntary self-sacrifice of someone in an attempt to save the victim, which causes ancient magic to protect the intended victim from the curse.

It should be noted that the Killing Curse is not the only spell that can kill a person; it is simply the most effective spell to use as it's effect is instant death. Other spells could also potentially kill a person, such as Fiendfyre or Sectumsempra, or a spell aimed at the heart, such as the Stunning Spell.

Survivors
Only one person is known to have survived the curse: the young Harry Potter was saved when his mother, Lily Potter, decided to block the curse herself instead of having her son killed. Later on, when Harry went to let himself be killed by Voldemort, the curse,, destroyed the bit of Voldemort's soul within Harry, but simply left Harry unconscious. He survived because he was letting himslef die to save the others at Hogwarts, and because it was conjured by the Elder Wand, which was loyal to Harry. When the curse used on Harry rebounded, Voldemort's body was destroyed, but, owing to his many Horcruxes, his spirit was unable to leave the physical world, and was later placed in a new body identical to his old one. The Phoenix Fawkes could also survive The Killing Curse. He swallowed one intended for Dumbledore, burst into flames, and was reborn from the ashes. It is debatable whether Voldemort could be said to survive the Killing Curse, as it backfired on him after hitting Harry, leaving him nearly dead but still alive.

Etymology
Avada Kedavra has been suggested to to have originated from the commonly used phrase "Abracadabra", which translates from Aramaic as "Begone like this word". It is much more likely to be based on the Aramaic אבדא כדברא avada kedavra, meaning I destroy as I speak, life being destroyed as the caster speaks the incantation. Both origins actually contradict the continuity of spells in the Harry Potter series that are derived from Latin terms.

Failed uses

 * Voldemort attempted to use the curse on Harry Potter as an infant - the curse was blocked by magical protection from his mother's sacrifice and somehow gave Harry some powers. Not only that, the curse backfired on Voldemort who barely survived.
 * Lucius Malfoy tried to use the curse on Harry Potter in Chamber of Secrets, but Dobby the house elf interrupted the spell with a powerful pushing charm.
 * Voldemort attempted to use the curse on Harry Potter during their duel in the graveyard, in Goblet of Fire . Harry's simultaneous Expelliarmus charm blocked Voldemort's curse and produced the Priori Incantatem effect, due to the common core in their respective wands (phoenix feathers from Fawkes).
 * Death Eater Antonin Dolohov attempted to use the curse on Hermione Granger towards the end of Order of the Phoenix but was disarmed in time by Harry Potter.
 * Voldemort attempted to use the curse on Harry Potter towards the end of Order of the Phoenix but was blocked by Dumbledore who transfigured a golden statue at the fountain in the atrium of the Ministry. In the ensuing duel between Dumbledore and Voldemort, Voldemort attempted to use it several times against Dumbledore but was blocked and resisted successfully each time. This is possibly due to Dumbledore's skill and his use of Elder Wand, which makes its user undefeatable in duels.
 * Vincent Crabbe attempted to use the spell on Hermione Granger and Ron Weasley in Harry Potter and the Deathly Hallows but the spell missed them both.
 * Voldemort used the curse on Harry Potter near the climax of Harry Potter and the Deathly Hallows. However, Harry survived, due to Voldemort using Harry's blood for his recreated body. With the protection Harry had from his mothers death also given to Voldemort, Harry could not die while Voldemort was alive.
 * In the same book, Voldemort later used the spell on Harry in a final attempt to kill him. Harry countered with Expelliarmus, mirroring the duel in the graveyard.  Voldemort's curse, however, backfired due to the Elder Wand refusing to kill its rightful master, Harry.  Thus, Voldemort killed himself.

Disputed uses

 * Bellatrix Lestrange killed a fox with a non-verbal spell after Apparating with Narcissa Malfoy at Spinner's End, thinking that it was a lurking Auror, but it is unknown whether it was the Avada Kedavra or some other lethal curse. There was a flash of green light however, indicating clearly that it was used.
 * Bellatrix Lestrange hit Sirius Black with a spell that made him fall into The Veil. It is not stated if the curse she used was Avada Kedavra, so it is disputed if it was the curse that killed him or him falling into the veil. However, in the film version of the Order of the Phoenix, Bellatrix Lestrange is shown using the curse and spoke the incantation, leading people to believe it was the killing curse.
 * A curse was used against Auror Alastor Moody in Deathly Hallows, resulting in his (supposed) death. Whether this was the Avada Kedavra Curse or not isn't known.
 * Molly Weasley actually killed Bellatrix Lestrange with a spell that struck her in the heart, but whether or not this curse was the Avada Kedavra is not mentioned at all in the book.