Throughout the 1996–1997 school year, Draco Malfoy would go to the washroom to find company with Moaning Myrtle, confiding the stress of his mission and fear of failing it.
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.
He didn't care about the bird. His tears were due to the fact that since the bird had died, he had failed once more to repair the Vanishing Cabinets. Draco needed to repair them in order to give the Death Eaters a safe way to infiltrate Hogwarts. Failure meant death, Voldemort had made that very clear.
First of all, Draco cries when the bird comes back dead. No, no, we're not saying that we like seeing Draco cry… eh, well, actually, maybe we are. See, it's proof that Draco isn't totally evil to the core.
Harry rushes to the bathroom where Draco is crying at the sink, sobbing that unless he does something soon, he will be killed. Draco spots Harry and pulls out his wand. Harry yells “Sectumsempra,” the hex scribbled in the margins of the Half-Blood Prince's book.
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.
Cruciatus Curse ('Crucio')
Repeated use of the Cruciatus Curse is torture and Bellatrix Lestrange subjected the Longbottoms to such extremes of pain that it sent them insane. 'Better dead than what happened to them,' was what Moody said of the Longbottoms' fate, and there's a sad ring of truth to that statement.
She asked him because if Draco was still alive, she had something to fight for. She had a reason to lie to Voldemort. If Draco is alive, she needs to get into the school to see him and protect him, and helping Harry feign death was the easiest way to do that.
In Half-Blood Prince, Katie is accidentally cursed by Draco Malfoy when she touches the cursed necklace that he intends to deliver to Dumbledore. Katie is transferred to St. Mungo's to recover for six months and is temporarily replaced by Dean Thomas on the Quidditch team.
Rowling commented that "The moment Draco got what he thought he wanted, to become a Death Eater, and given a mission by Lord Voldemort, as he did in Harry Potter and the Half-Blood Prince, reality finally hit him" because his dream was "so very different".
Snape knew that Harry had cast the spell on Malfoy because he had created the spell in the first place. He had probably used the spell many times and had even come up with a counter curse for it. It would be awfully sad if Snape couldn't tell when his own spell had been used on somebody.
The curse was invented by Severus Snape and recorded during his time as a student at Hogwarts, when he was known as "The Half-Blood Prince". He created it to retaliate against his enemies such as the Marauders, and he recorded it in his N.E.W.T.-level Potions textbook.
I've read many places that Narcissa Malfoy was never branded with the Dark Mark. Therefore, she was never an official Death Eater. However, she was privy to all of the secret plans of the Death Eaters; after all, Malfoy Manor was the headquarters for Voldemort and Co. during the Second Wizarding War.
Draco's First Year
He wears diapers and struggles with his fear of the potty throughout his first year, constantly mocked by his peers.
Despite being a valued Death Eater in the days before Voldemort fell following his attack on baby Harry, Lucius stumbled out of favor with the Dark Lord when he squandered Riddle's diary (secretly a horcrux) in Chamber of Secrets and failed to obtain the prophecy in Order of the Phoenix.
In some cases (the Malfoy family) blood traitors are a bad as Mudbloods. As other people said, it is also due to the Malfoys' arrogance, the feeling of self-importance and wealth. The Weasly family is also very poor, which may also lead to a dislike with the rich, pureblood families.
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.
Specifically, Draco was jealous of Harry. It was easy to miss because Draco didn't often show his emotions, modelling himself on his cold, confident, calculating father, but J.K. Rowling has confirmed that a lot of his enmity towards Harry stemmed from envy.
Draco says she suffers from a “blood malediction,” which ultimately ends up killing her the summer before Scorpius's third year. While it isn't clear that Astoria's and Nagini's conditions are the same, Draco's description of her illness seems to match up with new information from Rowling's tweets.
Pansy Parkinson
Draco lost his virginity to her on the Yule Ball night in fourth year and since then Draco and Pansy had been sexual partners.
The first time, it was his own mother dying for his sake, which created the magical protection that saved him. The second time, it was Narcissa's love of her own son which motivated her to lie to Voldemort, ensuring Harry's survival.
Draco had several reasons for lying to Bellatrix, including the fact that he was never a bad person. Moreover, he no longer found working for the Dark Lord appealing and hated how Voldemort treated his family. He did not intend to harm anyone and believed Harry was the only person capable of defeating Voldemort.
In Deathly Hallows, Hermione faced a real test of her physical and psychological stamina. After being on the run from a bunch of Snatchers, the gang were taken to Malfoy Manor, where Bellatrix proceeded to torture Hermione using the Cruciatus Curse.
The darkest of the Dark Arts, Harry Potter unforgivable curses are the Cruciatus Curse, the Imperius Curse, and the Killing Curse. Although the curses are highly illegal, Harry using Unforgivable Curses happened, but he uses them once he was thrust into the Second Wizarding War.