system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Would a child be able to use the killing curse successfully if they really meant to kill the target?

We know that the 3 unforgivable curses can only be successful if you utterly want to achieve what they are intended for (killing, causing pain, dominating somebody's will).

CrouchJr.-Moody tells his class that they could use Avada Kedavra on him and it would barely harm him, if at all. He also says there needs to be "a powerful bit of magic behind it", but it seems like even the least skilled of Voldemort's followers can use it.

After Bellatrix kills Sirius, she can only laugh about Harry's Crucio attempts. I can't say if the Killing Curse might have worked in that moment, because Harry surely would have wanted her dead.

My question is: If a wizarding child, like 11-13 years old, that saw a loved one murdered and knew the incantation Avada Kedavra and its effects, would they be able to kill the murderer by willingly using the Killing Curse?
gpt
It's theoretically possible, but unlikely. Putting aside the magical power which could be inherited and the skill which could be practiced, we come to a problem of "really meaning it".

The thing is, almost no 11 year old has an advanced enough conception of death and killing to mean it even if they want to. They have volition but lack understanding, real understanding of the magnitude of taking and destroying another life, not for a perceived injustice, not for a practical purpose, but just because you had the bloody-minded will to want to kill them.

Harry's failed crucio shows it is not as easy as hate. You have to be free of any good intent.