As every fan knows,
Lily Potter sacrificed her life in order to protect her infant son, Harry from Lord Voldemort. This placed Harry under magical protection, so that when Voldemort cast the Killing Curse at Harry in turn, the spell backfired, leaving him unharmed (save for a lightning-shaped scar on his forehead) and Voldemort bodiless.
He didn't know that Harry was protected. He might also have wanted to make an example of the Potter family. Avada Kedavra was his signature spell. An entire family being killed by a spell that even the worst wizards usually don't ever use once screams Voldermort.
He overheard part of the prophecy, and shared it with his master. Voldemort interpreted it to mean that Harry was destined to destroy him, and so he set out to find and kill him while he was a baby and, presumably, not yet a threat.
When Harry was hit by the killing curse as a baby, it rebounded and killed Voldemort, necessitating that he create a new body. This did not happen the second time.
In the final book, “Harry Potter and the Deathly Hallows,” Rowling reveals that Snape was acting on Dumbledore's orders and had protected Harry at school out of love for Harry's mother, Lily. “Snape died for Harry out of love for Lily,” Rowling said.
#1 Lily's Love, The Greatest Protection Charm
Love is the one thing that Voldemort is unable to handle and therefore when Quirrell was touched by Harry, he was burnt by the shield created to protect Harry as a result of Lily's love.
However, Voldemort chose Harry as his target, who was, like himself, a half-blood, rather than the pure-blooded boy named Neville. Voldemort chose Harry as he believed Harry was the most danger to him and he saw himself in Harry before even seeing him.
History Of Avada Kedavra
The Killing Curse was created in the early Middle Ages by Dark witches and wizards. Primarily, the curse was used to quickly slay opponents during a duel.
Her sacrifice gave Harry the power of love, a protection spell sealed with the blood spilled by her death.
As Rowling explained in a series of tweets, Snape loved Harry's mother, Lily, and his unrequited affection drove him to resent Harry's father, James — and by extension, Harry himself.
Voldemort wasn't aware of Harry being a pseudo-horcrux because he didn't plan it, and Harry didn't know either until Voldemort “killed” him, but he actually killed the piece of soul kept in him.
Though Harry encountered many opportunities that deemed Avada Kedavra necessary, it remains as one of the Unforgivable Curses Harry Potter never cast. For one, he viewed the spell as an immoral practice commonly used by users of the Dark Arts.
Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Through his faith in love and profound knowledge in tales, Dumbledore was able to foresee that Harry would be able to survive Voldemort during the final battle in Harry Potter and the Deathly Hallows. In addition, Dumbledore had faith that Harry would succeed in bringing peace to the wizarding world.
In order to preserve his position as a trusted Death Eater, Severus Snape was forced to tell Voldemort the true date at which the Order planned to move Harry, under the orders of Albus Dumbledore's portrait.
Who is immune to Avada Kedavra? Phoenixes were semi-protected from the Killing Curse, due to them being immortal. In 1996, Fawkes swallowed one intended for Albus Dumbledore, causing him to burst into flame and die instantly. However, he then was reborn from his ashes.
In order to conjure the avada kedavra curse, you have to want to kill your victim. We all know that Voldemort could easily kill a child without an ounce of remorse... but not Snape. Snape didn't want to kill Dumbledore, and this was why the spell was blue instead of the usual green.
Avada Kedavra meaning
Rowling claims she created this spell out of a popular “Abra-Kadabra” saying in Aramaic which means “Let the thing be destroyed”.
In the end, both were essential to Voldemort's downfall, fulfilling the possibility that both Harry and Neville were, in fact, the Chosen One. While Harry delivered the final blow to destroy Voldemort, Neville destroyed the final Horcrux which allowed Harry to end Voldemort.
While most fans agree that Harry is the unrefuted Chosen One, the final Deathly Hallows film (in particular) sways heavily toward highlighting a heroic Neville, revitalizing the debate regarding which boy is better suited for the iconic title.
Snape was revealed to have been in love with Harry Potter's mother, Lily, since childhood. That feeling lasted beyond her death, and into his own final moments. That's why it's so surprising that Snape became a Death Eater.
Quirrell's body manifests burns and blisters during his fight with Harry due to the protective power Harry's mother left in his skin when she died for him.
Voldemort hugged Draco as an improvisation and it wasn't planned. Even Tom Felton (Draco Malfoy) was caught unaware which increased the effect. In Harry Potter style, it was like a welcome for Draco, but as Voldemort had never known love, he didn't know how to hug him very well. Thats why they had the awkward hug.
It was just a coincidence.
Voldemort is planning the escape of his key lieutenants from Azkhaban and is alternately happy and frustrated. Those strong emotions make Harry's scar tingle. He also feels a similar pain when getting changed after Quidditch in Chapter 18.