At the end of the seventh book, Voldemort attempts to kill Harry with a Killing Curse, but the curse rebounds off of Harry and kills Voldemort instead. Harry survives due to the protection of his mother’s love and the sacrifice of his own blood.
Before Voldemort’s demise, he had finally obtained the Elder Wand, a powerful tool that was believed to be unbeatable. Voldemort had used this wand to force Dumbledore into a duel, in which Dumbledore was killed by Snape. Voldemort then claimed the wand as his own, believing it would make him invincible.
However, Voldemort did not understand the power of the wand and the circumstances surrounding it. He did not know that the wand would only obey its true owner, and that the only way to achieve that was to defeat its previous owner, which he had failed to do. Therefore, the wand never truly became his.
At the end of the battle, Harry and Voldemort faced off in a duel. Voldemort used the Elder Wand against Harry, but it had no effect on him. Harry then cast a spell, which was a variation of the Killing Curse. The spell was powered by the protection of his mother’s love and the sacrifice of his own blood. This spell was then reflected off of Harry, and struck Voldemort instead, killing him.
The protection that Harry had from his mother’s love was a powerful force, one that Voldemort had no defense against. This protection, combined with the sacrifice of Harry’s blood, allowed the Killing Curse to be reflected back at Voldemort, killing him.
Moreover, the wand was a factor in Voldemort’s defeat. Voldemort had failed to understand the power and significance of the Elder Wand, and thus it never became his. He had failed to defeat its true owner, and as a result, the wand was unable to protect him from the Killing Curse. The Elder Wand, in essence, had worked against Voldemort, allowing Harry to reflect the Killing Curse and ultimately kill him.
In the end, it was a combination of factors that resulted in Voldemort’s death. Harry’s protection from his mother’s love, the sacrifice of his own blood, and the power of the Elder Wand all contributed to the downfall of Voldemort. These elements allowed Harry to reflect the Killing Curse, killing Voldemort in the process.