When Harry critically injured Draco Malfoy with the Sectumsempra curse, it was actually enough to have him expelled, as Professor Minerva McGonagall stated Harry was lucky not to have been, due to Snape giving lenience to prevent others from finding out that he was the one who invented the curse.
There is likely a good reason that the Sectumsempra is not an unforgivable curse. It's mostly because Sectumsempra is Snape's personal curse that he created. It is not a widely known or used spell, and it is one that he kept secret — which means it can't be added to the list since no one really knows about it.
The spell requires controlled use, which implies practiced use, and after slicing up Draco the way he did I doubt Harry made much if any use of Sectumsempra. He's not especially bloodthirsty and may never have realized that it could be used with finesse, so he wouldn't have much use for the spell.
What was Snape's reaction to Harry using Sectumsempra?
Later that night, after Snape killed Dumbledore, Harry attempted this curse against him multiple times, only for Snape to block it repeatedly and angrily reveal to Harry that he was its inventor.
Why Sectumsempra Isn't an UNFORGIVABLE Curse - Harry Potter Theory
How did Snape heal Draco from Sectumsempra?
Vulnera Sanentur was the song-like incantation of a healing spell which was used to heal deep wounds, which could also be used as the counter-curse for the curse Sectumsempra.
Harry Potter's use on Draco Malfoy in the Duelling Club. The Tickling Charm (Rictusempra), also known as the Rictusempra Charm, is a spell that causes a victim to buckle with laughter. It also has at least two other side effects on the victim. It is usually used as a diversionary tactic in duels.
Harry Potter used Unforgivable Curses, such as the Cruciatus Curse, in extreme situations of emotion and distress. Harry used the Imperius Curse multiple times during the Gringotts heist to accomplish their mission.
After the Wizards' Council was reformed into the Ministry of Magic, tighter restrictions were placed on the use of certain kinds of magic. The Imperius Curse was deemed by the Ministry to be Dark magic, and, along with the Cruciatus and Killing Curses, were declared "unforgivable" in 1717.
Draco is in his own house. He is his godson and the child of his good friend Narcissa and fellow former death eater Lucius. He is fond of Draco if you could call it that. He doesn't like Harry at all.
In the final movie, Harry Potter and the Deathly Hallows pt. 2, Molly first hits Bella with a spell that freezes her, most likely Petrificus Totalus. Then, she launches another one that shatters her entire body into pieces, which could be expelliarmus, bombarda, stupefy, or any spell that can produce such an effect.
When Death Eater Bellatrix Lestrange killed Harry's godfather Sirius Black, Harry chased down Bellatrix and performed the curse on her out of rage. However, it was performed unsuccessfully as Harry was doing it with "righteous anger" and couldn't muster the will to actually cause her harm.
Although it is not confirmed to have been the Killing Curse, it is highly likely that Ron attempted to kill Voldemort's snake, and last Horcrux, Nagini, with Avada Kedavra. This is because, in the movies, Ron can be seen firing out a green spell at the snake, and it looks just like the Killing Curse.
The injury was caused by Snape's Sectumsempra spell in order to stop the Death Eaters from hurting George (who he thought was Harry) and Lupin, but missed and hit George. Hermione and Kingsley then arrived, both unharmed, followed by Arthur and Fred Weasley, both concerned for George.
During the Battle of Hogwarts, Voldemort used the Cruciatus Curse on what he believed to be Harry Potter's dead body as a way of dishonouring it and to show he had won. Harry felt no pain because the wand Voldemort used, the Elder Wand, refused to harm its true master.
Family. Snape's family background is mostly shown in flashbacks during the course of the last three novels. Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince").
They were tools of the Dark Arts and were first classified as "Unforgivable" in 1717, with the strictest penalties attached to their use. The three curses consisted of the Killing Curse (Avada Kedavra), the Cruciatus Curse (Crucio), and the Imperius Curse (Imperio).
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.
In the film, Bellatrix casts a blue spell at Ginny Weasley instead of a Killing Curse, who deflects it using a Shield Charm. In the book she just avoids it.
They know she's an impostor. They've been warned", so obviously the request for the wand was unexpected even to him. It's thus pretty safe to conclude that the real Bellatrix had reported her wand stolen and alerted Gringotts prior to the trio's attempted break in.
However, despite being rescued by them, Griphook's general mistrust of wizardkind resulted in him betraying Harry Potter, Ron Weasley, and Hermione Granger. He betrayed them because he believed they would not hand him the Sword of Gryffindor, after destroying the Cup and other Horcruxes.
He used the Cruciatus Curse against Bellatrix (failed), Severus (deflected) and Amycus (succeeded.) Though, of course, as our fair McGonagall said, when Harry used the torture curse it was actually gallant. Not Dark Magic, but chivalry. Harry never used the Killing curse.
The charm was invented by Severus Snape and recorded during his time as a student at Hogwarts School of Witchcraft and Wizardry, meaning it would have been created sometime between 1971 and 1978.
