Reposting my Nagini analysis here. It deserves to be on my main blog and as more than just a reblog.
Fantastic Beasts tells us that Nagini as a Maledictus, was considered an 'underbeing', which means she could not do magic even in her human form.
From Fantastic Beasts: The Crimes of Grindelwald
Voldemort and the Purebloods he championed hated people like Nagini and oppressed them. Nagini was acutely aware of that. She even tried to hold Credence back from joining a cause championed by Purebloods because it oppressed people like her and Credence.
From Fantastic Beasts: The Crimes of Grindelwald
Yet, because of her curse, she ended up losing that highly conscious mind and all her agency. The snake she never wanted to become ended up serving the very cause she was resisting.
By the time Voldemort acquired Nagini, she was nothing but a snake who had lost her former human mind, according to JKR.
Slowly, over time, they are turning into a creature and they can't stop it. They can't turn back. They will become a beast. With everything that implies, they will lose themselves. They'll be alive but in beast form whereas an Animagus retains their human brain.
- J. K. Rowling about Nagini in the CoG Blu-ray Special Feature Credence, Nagini and the Circus Arcanus.
Voldemort exploited Nagini's snake form for all it was worth. Her venom was special with properties akin to unicorn blood and Voldemort wanted it, just like he wanted unicorn blood and the Philosopher's Stone. Nagini lost her human mind after her transformation, which allowed Voldemort to exploit her without the resistance her human self would have offered. Even her magical link with Voldemort was a result of the very exploitation her human form constantly resisted and was highly conscious of. Unlike with unicorn blood, he did not need to kill her to acquire her venom. The Horcrux link made her completely obedient to him and curbed any resistance her snake form might have offered as well.
From Harry Potter and the Half-Blood Prince
Because Vodemort chose to go after the Philosopher's Stone instead of using snake venom after finding Quirrell, it can be deduced that an ordinary snake would not have sufficed and Nagini carried something life-giving in her venom. She was most likely immortal because of her curse, which is why she lived for over a century and did not die a natural death. That symbolism alone makes her a perfect choice for a Horcrux by a man obsessed with immortality, and the choice had practical uses too, for it made her a perfect weapon and completely obedient to Voldemort. Dumbledore was correct that it also underlined his Slytherin connection and enhanced his mystique, which is why he constantly used Nagini to intimidate his Death Eaters.
Making her a Horcrux was a very exploitative thing to do because he was using a living being as a weapon, overriding her own will and agency with his, making her a target, and extracting the venom she produced. He did all that while dehumanising her and referring to her with impersonal pronouns in his private thoughts.
It can thus be deduced that using personal pronouns for her in front of other people was a calculated choice made to instill fear in their hearts.
He used Nagini as a weapon and an attack dog. She attacked Arthur Weasley in OOTP, disposed Charity Burbage's body in DH, and was sent to capture Harry in the same book. It was all very utilitarian. While he showed some affection to Nagini, it was very surface-level. Compare it to FIlch, who showed much more attachment to Mrs Norris than Voldemort ever showed towards Nagini.
When Filch thought Mrs Norris had died, he was devastated and ready to kill Harry.
From Harry Potter and the Chamber of Secrets
Look how hysterical Filch is over his cat. He is sobbing and wants to avenge her. He acts like any normal person who thinks their beloved pet has been killed would.
Voldemort, on the other hand, saw Nagini die in front of his eyes and did not even attempt to kill Neville. He just screamed, even though she was a Horcrux. That is how little he cared about Nagini. He only exploited her snake form for his own benefit, and when it was killed, he barely cared.
From Harry Potter and the Deathly Hallows
The only death that affected Voldemort was Bellatrix's, who was a pureblooded human witch. Hers was the only death that made him lose control of himself and attempt to avenge it. He tried to kill Bellatrix's killer but never Nagini's.
From Harry Potter and the Deathly Hallows
He shows all the hallmarks of grief there that Filch also shows when he thinks Mrs Norris is dead, only much more stoically because his emotions are inherently filtered through his stoicism and many walls. That does not mean they are not there.
They both screamed and lost control of themselves. Filch sobbed and Voldemort's magic exploded, throwing off three powerful duellists. Voldemort nearly killed Molly and Filch threatened to kill Harry.
Nagini is perhaps Voldemort's most tragic victim. It's entirely possible that Voldemort was genuinely fond of her snake form, but from her own perspective, the story is of tragedy and exploitation by the very people her human form was resisting.
The question it personally raises for me, though, is whether exploitation can even exist when the victim's humanity no longer does. It's true that human-Nagini and snake-Nagini share the same body and soul, even if the mind has changed, and Voldemort benefitted from the very loss of agency the human always resisted. I suppose it could be similar to exploiting someone with dementia in ways their former self would have rejected, and Nagini's human self would absolutely have been horrified by her servitude to Voldemort's cause.
Yet, since she possesses no human consciousness after her transformation and is cognitively just a snake, then what, precisely, is being exploited? A snake cannot have ideologies, after all, and we don't really characterise, say, guard dogs as exploited, even when treated purely as utility. The tragedy, then, lies in the transformation itself and what was irretrievably lost for the human.
The answer, to me, is open-ended.