Harry makes use of two of the Unforgivable Curses in the books. Dueling with Bellatrix Lestrange, he attempts the Cruciatus curse, with limited results; Bellatrix says that he has to really hate someone to make the Unforgivable Curses work properly, righteous indignation isn't enough.
Harry truly realizes this when he casts the Cruciatus Curse on Amycus Carrow after Carrow spits in the face of Professor McGonagall in the Ravenclaw dormitory, stating his understanding of the anger one must feel to make such a curse be effective.
Cruciatus Curse ('Crucio')
Harry tried to use this spell himself. The first time was against Bellatrix after she had killed Sirius. His attempt was unsuccessful because, as Bellatrix mockingly explained: 'You need to really want to cause pain – to enjoy it – righteous anger won't hurt me for long…'
Avada Kedavra - Used 8 times.
It is common to see this curse used by the Death Eaters and by “He Who Must Not Be Named.” This spell is based on the Aramaic, meaning "disappear like this word."
The three Unforgivable Curses are the Cruciatus Curse, which causes unbearable pain; the Imperius Curse, which allows the user to control the actions of the victim; and the Killing Curse, which causes instant death.
Harry makes use of two of the Unforgivable Curses in the books. Dueling with Bellatrix Lestrange, he attempts the Cruciatus curse, with limited results; Bellatrix says that he has to really hate someone to make the Unforgivable Curses work properly, righteous indignation isn't enough.
Avada Kedavra, also known as the Killing Curse, kills a person instantaneously and without injury. There is no countercurse for it, and only one person, Harry Potter, has ever survived it.
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
Expelliarmus did not beat Avada Kedavra.
Voldemort's wand (the elder wand) recognized its true master (that was Harry) and refused to attack it. In a way Voldemort killed himself as his own spell backfired on him.
None of the good guys dare use the Killing Curse throughout the events of the movies and books, no matter how high the stakes and how difficult things are. But Ron Weasley is the exception, giving it a go in the Deathly Hallows: Part 2 movie when himself and Hermione look destined to die via Nagini.
The least-used spell: Waddiwasi, used in Harry Potter and the Prisoner of Azkaban, which is “the incantation of a charm that can be used to shoot a small, soft mass of whatever the caster so desires at the target or victim,” according to the Harry Potter Wiki.
Confringo. Commonly known as the Blasting Curse, Confringo causes the target to explode. To make it even more dangerous, it produces flames that ignite upon contact with the target. If Confringo fails to kill the target immediately, they will instead suffer a slow and painful death.
Malfoy spots Harry and casts a Cruciatus curse; Harry, defending himself, using the Half-Blood Prince's Sectumsempra spell without knowing its effects. To his horror, it gashes Draco's face and chest, spilling his blood everywhere. Moaning Myrtle flies off, screaming.
Dec. 28, 1997: Ron Weasley destroys Salazar Slytherin's locket deep in the Forest of Dean, Gloucestershire, by stabbing it with Godric Gryffindor's sword.
And while many fan-favorite characters have fallen victim to the Killing Curse, one surprising figure working at Hogwarts School of Witchcraft and Wizardry may possess limited immunity from the spell's full, lethal effects: Rubeus Hagrid.
At the end of Fantastic Beasts 3 though, Grindelwald attempts to use Avada Kedavra on Credence, but Albus and Aberforth Dumbledore successfully block it using golden magic.
This means that the killing curse (if I'm correct) has the power to destroy horcruxes. But when Ron and Hermione are about to die by Nagini, Ron casts the killing curse as a last resort and it simply rebounds off Nagini as it was nothing.
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. In 1707, the Wizards' Council was restructured into the Ministry of Magic, which allowed for more strict restrictions on certain types of magic.
Narcissa's greatest moment, however, was when she chose to betray Voldemort in Harry Potter and the Deathly Hallows. Not knowing whether Draco was alive or dead, Narcissa chose to lie to the Dark Lord rather than risk losing her son.
They were first classified as "Unforgivable" in 1717. They are the Killing Curse, Avada Kedavra, the Cruciatus Curse, Crucio, and the Imperius Curse, Imperio.
Additionally, in Harry Potter and the Chamber of Secrets, Professor Dumbledore looks right at Harry and Ron underneath the Invisibility Cloak while in Hagrid's hut, suggesting that Dumbledore might actually be able to see through the Invisibility Cloak.
Horcruxes can only be destroyed in specific circumstances that allow it's complete and utter destruction. In the movies, the horcruxes are destroyed in these ways: The killing curse — “Avada Kedavra.” Fiendfyre — a curse that creates powerful and magical flames.
According to J. K. Rowling during a web chat, the lightning scar no longer burnt or hurt after Voldemort's defeat. J. K. Rowling stated that the pain from Harry's scar on his forehead was caused by the piece of Voldemort's soul trying to leave his body through the wound it entered to rejoin its master's soul.