Albus Dumbledore on Voldemort's bond with Nagini. Voldemort had a special relationship with Nagini, as she was his pet and one of his Horcruxes. According to Dumbledore, Voldemort had strong feelings for Nagini that he had not for anyone else; she was the one living thing that he had ever cared about.
Why did the killing curse work on Harry but not Nagini?
As long as Voldemort lives, Nagini is invulnerable to mortal death except by the methods known to destroy Horcruxes: basilisk venom or fiendfyre. It works differently with Harry because he is not a true Horcrux.
Nonetheless, despite her initially benevolent nature, Nagini's blood curse eventually turned her into a snake permanently. Though it is unknown if she became evil as a result of that, or was turned evil as a result of Voldemort turning her into a Horcrux. As a snake, Nagini was completely loyal to Lord Voldemort.
Delphini was born in secret at Malfoy Manor in early March 1998 as the result of a liaison between Bellatrix Lestrange and Lord Voldemort. On 2 May 1998, both of her biological parents were killed in the Battle of Hogwarts.
Of course, Voldemort was a Parselmouth, and this was the root of his friendship with Nagini. Much like Grindelwald did with Credence, it's likely Voldemort gave Nagini a false sense of belonging after she had been trapped in a snake's body for possibly decades.
Simple answer is, that's only in the movies. They often play fast and loose with things that might look or sound cool in the moment but make no sense in the overarching story. Ron never casts Avada Kedavra at Nagini in the books.
The author explicitly states that both women were fighting to kill, despite Molly refraining from casting the Unforgivable curse Avada Kedavra. The result of the duel actually comes about as a result of nothing more than spectacular accuracy on Weasley's part.
In this book, Rowling reveals that Bellatrix is the guardian of Helga Hufflepuff's cup (though she is unaware that it is a Horcrux), which Voldemort has entrusted the Lestranges to keep in their Gringotts vault.
The prophecy is mentioned throughout the series, however, it never exclusively mentions that Harry is The Chosen One and suggests Neville was another option. However, one theory explains why, in reality, this wasn't possible.
Behind the scenes. When Harry and Hermione are on the first floor of Bathilda's house, Nagini (inside the corpse of Bathilda) tells Harry to 'Come! ' from the next room in Parseltongue. In reaction, Hermione jumps and clutches Harry's arm, and the two of them obey the command.
But now we know Nagini was no simple supervillainous pet, but a human woman cursed with the “Maledictus” blood curse, which, according to Rowling, is a female-only inherited condition which grants the affected individual the ability to transform into an animal at will, until one day, the transformation becomes ...
This was revealed in The Fantastic Beasts and Where to Find Them franchise and has ignited many questions about Nagini and Voldemort's relationship. People believe Voldemort might have met Nagini during his time without a body in Albany many years after she turned into a snake, which led to their unusual bond.
Notably, Voldemort appeared to be entirely unaware of this split, as he later created a seventh Horcrux in his quest to have six, and continued to target Harry Potter despite him now holding part of Voldemort's own soul.
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.
It did backfire on Voldemort but just not the degree it did the first time. It failed to destroy his body because it killed the piece of hit soul that was in Harry forming the horcrux but it did knock him off his feet and actually rendered him senseless.
It is also said to be a fairly complicated spell. It depends on a persons willingness to kill someone and also the power behind the wand. To quote Barty Crouch/Mad-Eye Moody in 'Harry Potter and the Goblet of Fire', “Avada Kadavra is a curse that needs a powerful bit of magic behind it.
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.
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.
Many would be shocked to know that the Head of Gryffindor House Minerva McGonagall uses one of the Unforgivable Curses in the Harry Potter books, though it's not depicted in the movies. In Harry Potter and the Deathly Hallows, Harry is followed up to Ravenclaw Tower by Death Eater Amycus Carrow.
The prevailing theory has been that Voldemort gradually lost his nose (and humanity) throughout his life due to his exclusive use of Dark Magic. The more Dark Magic he tapped into, the less human he became both figuratively and literally. This was only amplified as he split his soul to create the Horcruxes.
Fans are left wondering how Delphini came to be — did Voldemort have a secret love affair or was she conceived using a love potion? Despite Bellatrix's obvious feelings for Voldemort, there was no real love connection between them, as Voldemort was incapable of love due to his soul being fragmented through Horcruxes.
In Harry Potter and the Cursed Child, it is revealed that Bellatrix gave birth to Voldemort's daughter Delphi in Malfoy Manor before the Battle of Hogwarts.
