Why didn’t Harry use “Avada Kedavra” in the final duel?

Question

In Deathly Hallows: Part 2, in the final duel between Harry and Voldemort, Harry only tried to disarm Voldemort.

Why didn’t he use “Avada Kedavra”?

Answer 1

I don’t believe there is a definitive canon answer to this, but here are some plausible reasons:

• Experience. The disarming charm is Harry’s signature spell, and he has a lot of experience using it. By contrast, he’s never used Avada Kedavra, far less in a combat situation.

  His other uses of Unforgivable Curses have had mixed results: although he used the Imperius curse successfully while breaking into Gringotts, his initial attempts to use the Cruciatus curse on Bellatrix and Snape were unsuccessful. (Though as @quapka points out in the comments, he did eventually gain competence in this curse.) In such an important fight, risking a new and untested spell seems unwise.

• Reliability. He’s used a disarming charm on multiple occasions to great effect, including the Battle of the Seven Potters and his last duel with Voldemort, in Goblet of Fire. Indeed, the book acknowledges that a disarming charm is what gives him the best chance:

  Harry heard the high voice shriek as he too yelled his best hope to the heavens, pointing Draco’s wand:

  “Avada Kedavra!”
  “Expelliarmus!”

  _{— Deathly Hallows, chapter 36, The Flaw in the Plan}

  Why break what works? Of course, this is tied to the experience aspect.

• Mercy. In the books, we learn that an act of great remorse may repair a soul which has been split using horcruxes, and Harry offers Voldemort this chance for redemption:

  “Yeah, it did,” said Harry. “You’re right. But before you try to kill me, I’d advise you to think about what you’ve done… Think, and try for some remorse, Riddle…”

  “What is this?”

  Of all the things that Harry had said to him, beyond any revelation or taunt, nothing had shocked Voldemort like this. Harry saw his pupils contract to thin slits, saw the skin around his eyes whiten.

  “It’s your one last chance,” said Harry, “it’s all you’ve got left… I’ve seen what you’ll be otherwise… Be a man… try… Try for some remorse…”

  _{— Deathly Hallows, chapter 36, The Flaw in the Plan}

  Using a disarming charm rather than a killing curse offers Voldemort this final chance. It isn’t Harry who kills Voldemort; it’s the curse which came from the wand that Voldemort was holding. I think Harry would want to give Voldemort that final chance.

• Not descending to Voldemort’s level. Remember that Harry wants to pursue a career as an Auror, and the first Auror he “met” was Moody. In Goblet of Fire, we learn that Moody tried to minimise deaths, and Harry may well have been influenced by this:

  “I’ll say this for Moody, though, he never killed if he could help it. Always brought people in alive where possible. He was tough, but he never descended to the level of the Death Eaters.”

  _{– Goblet of Fire, chapter 27, Padfoot Returns}

  I can’t think of specific references, but I think Dumbledore would likewise have preferred Harry not kill Voldemort if at all possible. He looked up to them both, and that might have influenced his plan for the final duel.

  Voldemort was surely destined for execution either way, but that doesn’t mean Harry has to be the one to give the fatal blow.

Answer 2

I think alexwlchan's answer is very detailed and gives good explanation. To support his reasoning I may just add this:

Harry is not a killer

Rememeber how Harry treated Peter Pettigrew in the Prisoner of Azkaban:

“NO!” Harry yelled. He ran forward, placing himself in front of Pettigrew, facing the wands. “You can’t kill him,” he said breathlessly. “You can’t.” Black and Lupin both looked staggered.
...
“We’ll take him up to the castle. We’ll hand him over to the dementors.... He can go to Azkaban... but don’t kill him.” “Harry!” gasped Pettigrew, and he flung his arms around Harry’s knees. “You — thank you — it’s more than I deserve — thank you —” “Get off me,” Harry spat, throwing Pettigrew’s hands off him in disgust. “I’m not doing this for you. I’m doing it because — I don’t reckon my dad would’ve wanted them to become killers — just for you.”

And the second time in Malfoy's Mansion in the Deathly Hallows:

“No —”
Without pausing to think, Harry tried to drag back the hand, but there was no stopping it. The silver tool that Voldemort had given his most cowardly servant had turned upon its disarmed and useless owner; Pettigrew was reaping his reward for his hesitation, his moment of pity; he was being strangled before their eyes.

“No!”
Ron had released Wormtail too, and together he and Harry tried to pull the crushing metal fingers from around Wormtail’s throat, but it was no use. Pettigrew was turning blue.

Another situation is at the Tottenham Court Road:

“What are we going to do with them?” Ron whispered to Harry through the dark; then, even more quietly, “Kill them? They’d kill us. They had a good go just now.” Hermione shuddered and took a step backward. Harry shook his head.

“We just need to wipe their memories,” said Harry. “It’s better like that, it’ll throw them off the scent. If we killed them it’d be obvious we were here.”

As discussed in this question, casting Avada Kedavra is not a easy daily spell. There is a lot behind it, mostly the fact, the you must intend to kill without hesitation and remorse. I am not saying, Harry did now have a reason to kill Voldemort. But he was not that kind of person. He did no try to kill Voldemort in the Graveyard and he did not do it at the end.

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The association with Avada Kedavra

Another example, why Harry would not use Avada Kedavra might be, that it represented the way his parents died. I think almost every mention of that Curse might recall him that event. Imagine him using the Curse which killed his parents, even if it was on Voldemort, how would he feel about it? For that I'd quote three paragraphs from the Goblet of Fire:

• How Voldemort had killed Harry’s father first. How James Potter had tried to hold him off, while he shouted at his wife to take Harry and run... Voldemort had advanced on Lily Potter, told her to move aside so that he could kill Harry... how she had begged him to kill her instead, refused to stop shielding her son... and so Voldemort had murdered her too, before turning his wand on Harry....

• They were talking about the lesson, Harry thought, as though it had been some sort of spectacular show, but he hadn’t found it very entertaining — and nor, it seemed, had Hermione.

• “Some lesson, though, eh?” said Ron to Harry as they set off for the Great Hall. “Fred and George were right, weren’t they? He really knows his stuff, Moody, doesn’t he? When he did Avada Kedavra, the way that spider just died, just snuffed it right —” But Ron fell suddenly silent at the look on Harry’s face and didn’t speak again until they reached the Great Hall

It is true, that against this argument might stand the fact of him using Cruciatus Curse, even though he's seen Neville's parents. But I think the representation might not be that strong.

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Last bit

As @Mooz pointed out in the comment, I also believe, that Harry is not a killer. But I feel, that this should be here too:

“I’d want him finished,” said Harry quietly. “And I’d want to do it.” “Of course you would!” cried Dumbledore.

...

He will continue to hunt you... which makes it certain, really, that —”
“That one of us is going to end up killing the other,” said Harry.
“Yes.”

_{Half Blood Prince, chapter 23, Horcruxes, page 512.}

Answer 3

A disarmed wizard is as defeated as a dead one, you can easily execute him later.

Ex-Pel-I-ar-Mus is shorter than A-va-da-ka-dav-ra. You get 6/5th as many spells cast that way.

Harry would be more familiar with the gestures. In the movies, two people casting a spell on each other the spells seem to push each other away, I assume the books were similar, been a while since I read them. If he gets the gesture wrong to Avada Kedavra, he has no defence and will die. Better to go with what you know.

Also, the good guy shouldn't kill and all that.

Answer 4

Non-canonical: Harry is the good guy, he can't just kill Voldemort straight up.

Canonical: Why shouldn't he? Expeliarmus has worked out pretty well for him so far. He matched Voldemort's Avada Kedavra at the end of Goblet of Fire with Expeliarmus, and it worked. Even after the deatheaters recognized Harry because of using Expeliarmus (book 7 transport of Harry to the Burrow - chapter 4, The Seven Potters), Harry continued to use Expeliarmus quite successfully.

Furthermore: To use Avada Kedavra is still a crime, no matter who uses it and, more importantly, who it's used upon. Althought I don't think this is Harry's main objection (after all he uses Crucio several times)

Answer 5

Harry already had experience with this particular combination of spells (Avada Kedavra + Expelliarmus).

At the end of Goblet of Fire, in the cemetery, it was this same combination that activated Priori Incantatum. The requirements for Priori Incantatum is that the wands must be brothers:

"So what happens when a wand meets its brother?" said Sirius.
"They will not work properly against each other," said Dumbledore, "If, however, tho owners of the wands force the wands to do battle...a very rare effect will take place. One of the wands will force the other to regurgitate spells it has performed -- in reverse. The most recent first....and then those which preceded it...."

GOF, US HC p. 697

When did this happen?

"Voldemort was ready. As Harry shouted, "Expelliarmus!" Voldemort cried, "Avada Kedavra!"

GOF, US HC p. 663

So, Harry's knowledge and experience presents two possibilities:

1. Harry had surmised that he was the master of the Elder wand, and thus knew the wand would not want to work against him. Similar to how brother wands to not want to work against each other. Therefore, he may have guessed a similar phenomenon would have occurred. (That is, the wand not letting something happen).

2. This battle was meant to be the conclusion to the battle that started in the cemetery. In the first battle, Harry wasn't ready to face Voldemort. He ended up having to flee. This time, Harry wouldn't flee, and he would defeat Voldemort the same way he'd tried to years ago.

Aside from these points, we must also address why Harry decided to this particular non-lethal spell, as opposed to others such as Stupefy or Petrificus Totallus. There are several reasons to specifically use Expelliarmus:

• Other spells, which may have temporarily incapacitated Voldemort, could have been undone by Death Eaters, or possibly by Voldemort himself using a Nonverbal spell (if he were still conscious).
• The disarming spell would have specifically taken away Voldemort's powerful wand. Even if he were to use a Death Eater's wand after that, it wouldn't be the Elder Wand. Also, the time between disarming & rearming Voldemort could be used to decisively defeat Voldemort.
• Harry knew he was the Elder wand's master, and thus the Elder wand would want to return to him. This increased the chances of this spell being effective, because the Elder want did not want to be in Voldemort's possession.

When we look at all these pieces together, I think it's possible to conclude that Harry had to use Expelliarmus. His personal character and morals dictated not using Avada Kedavra in general, but there was much more going on with his choice of disarming instead.

Answer 6

It needs practicing: when Crouch-as-Moody demonstrates it, he says that the whole class could use it on him and he'd get barely a nosebleed.

But it's also irrelevant to Harry: he knows the Elder Wand won't kill him - he spends about 2 pages of the book explaining that to Riddle and the crowd - so he doesn't need such a drastic measure to defend himself. The question is why he needs to defend himself with Expelliamus even: he could just lower his wand and let his opponent's arrogance do the work for him for the second time in a couple of hours.

What Harry is really trying to do is save Riddle's soul. Remorse is the only method of repairing the damage created by making a horcrux, but can kill. In Riddle's case, who only has one-ninth of a soul after the death of Nagini, Harry can be fairly certain of it - so he will get vengeance anyway. But he has seen Riddle's future if he dies without remorse and feels both pity and revulsion, and that he must give Riddle the opportunity for one last chance.

Answer 7

Remember what Harry was taught about the Horcruxes. In order to create one you have to kill and killing fractures a soul, that is how Voldemort could embody a horcrux, it contained a piece of his soul. Harry wouldn't want to do that to himself.

Harry's most effective weapon against all the battles with Volemort was love. The love of his mother saved his life as a baby, all the way through the spirits of his loved ones standing with him as he realized he had to sacrifice himself to Voldemort in the woods to fulfill the prophecy.

When Harry meets with Dumbledore in the "spirit" King's Cross Station and asks what was under the seat and Dumbledore told him not to bother with it. I believe it was the part of Voledmort's soul attached to Harry when Harry was made into a Horcrux by mistake as a baby.

Just my thoughts on it.

Answer 8

The Elder wand belongs to Harry
Harry knows at this point that the Elder wand is his, and Voldemort is using it against him. This means that the wand mustn't want to fight against him, and will probably turn to him.

Answer 9

I believe that the lingering protection in both Harry and Voldemort( Lily's protection lives in them both after Voldemort uses Harry's blood to restore his own body) is the reason that Harry knew not to use the killing curse. It was definitely not necessarily, and quite inadvisable to do so. I also believe that, even if he could use it, he wouldn't.

Answer 10

In my opinion Harry didn't use the Killing Curse for he doesn't have experience performing it. He would have obviously used the Disarming Charm because it was the spell he had been able to master, therefore, it became his signature spell.

Answer 11

Also the simple answer, that Harry was a thump'in good wizard according to all the books, but any real "dark" power such as his ability to cast Sectumsempra in "Half Blood Price," came from the shard of Voldemort's soul all the years Harry carried it as a horcrux, that was what gave him the ability to speak Parseltounge. Once Voldemort killed Harry and thus the shard of himself in Harry making him no longer a horcrux Harry lost the abilities that the shard of Voldemort's soul had given him, no more Parseltoungue, no more dark abilities. Even with a chunk of Voldemort in him he could not even cast a Crucio on Bellitrix just after she killed his last remaining family. And that was with Voldemort inside him, after the destruction of the horcrux within him he was just a normal wizard with no special powers. Aveda Kedavra was probably not even possible.

Answer 12

Because Harry won't Use The Curse That His Parents Got Killed With It

But That is Fool thing from him because he use the weak curse like disarm curse and shocking curse and those kind of things.