How did Harry kill Voldermort?

[Najma]

All I remember is, Harry hits voldermort with an expelliamus and somehow volermort's own spell backfires him. How did that happen? And why didn't harry simply kill him with avada kedavda or some other method?

[Silver]

It was because Voldemort was using the elder wand, but the elder wand didn't respond to him, it responded to Harry due to some long and complicated reason of how it came to be in Harry's possession. This is the reason why the spell backfired and Harry was able to kill Voldemort.

[Najma]

Silver wrote: "It was because Voldemort was using the elder wand, but the elder wand didn't respond to him, it responded to Harry due to some long and complicated reason of how it came to be in Harry's possession..."

In that case, Harry must have known beforehand that he possessed the elder wand, or else, he wouldn't take risk by simply trying to disarm voldermort.

[Megan]

ThePirate74 wrote: "In that case, Harry must have known beforehand that he possessed the elder wand, or else, he wouldn't take risk by simply trying to disarm voldermort."
Yeah, because he realised that Draco disarmed Dumbledore and Harry disarmed Draco. And I think he knew that because Dumbledore got the wand from Grindlewald and Grindlewald was still alive. Thus, Harry could get the wand by disarming instead of killing. But it never really lays that out very clearly to the reader, so I could be way off.

[Ruby]

It makes sense but it often takes a lot of explaining to make sense. I'll try:

1) Harry truly believed that he would have to fight Voldemort in the end. EXHIBIT A: right before he fought him in the Great Hall, he said- "It's got to be me." This was in part due to him knowing the prophecy about he and Voldemort fighting each other and one of them dying in the end.
2) Harry did indeed know that he was the true owner of the Elder Wand- he explains how and why he knows this as he and Voldemort circle around each other and do some bantering. He says, "...I am the true owner of the Elder Wand." The Elder wand, like Silver said, didn't really respond to Voldemort ever because he had never really won it from anyone in any way the wand understood.
3) The Elder Wand cast the Avada Kedavra spell but then flew up in the air and Harry caught it. I believe that Harry's expelliarmus spell is what caused this.
4) I quote: "Lord Voldemort was dead, killed by his own rebounding curse." The AK curse rebounded on him after he cast it either because it hit Harry's spell or because the Elder Wand cast it wrong.

In any case, it really should have been made a little more clear, seeing as how the result was so confusing. Even if it does make sense in the end, JK could have spelled it out- no pun intended- better in the first place.