(Probably) unpopular headcanon about Bellatrix
Growing up she was the most responsible of all of the sisters. Maybe she didn’t see the error in her parents’ ways, but she did see how they hurt her sisters, and so she basically tried to take all the blame for everything and take all the beatings etc, to try and let Andromeda and Narcissa have the nest childhood they could. It broke her when she had to go to hogwarts and leave them unattended for those many years before they were finally there, too. She would do all the chores and be the one trying to “fix” the family.
Because of this, when they were all finally out of the house, she found no interest in having children despite her being taught that it was a woman’s duty to her husband. Instead, she felt she needed to be devoted to something that needed her as much as her sisters had, and through that she found Voldemort and the Death Eaters.
She might not have been entirely sane back then, because who would be after seventeen years of being with Druella and Cygnus playing medieval dollhouse, but she was on a functioning level in her head when she knew where to quit, when to stop, how to hold herself together in front of people.
When she first started her career as a Death Eater, she became very accustomed to using the killing curse instead of imperio or crucio because it was faster and more humane that way, and it maintained her humanity a little bit. But then the day came where she was forced to use crucio.
But when she was sent to the Longbottoms’ house, it broke her. She looked in the window and saw such a happy family, laughing and holding their little baby as one read a book and the other clicked on the telly.
She didn’t want to go inside there and ruin that. She didn’t want to kill them. She didn’t want that boy to grow up without that mother and father that so doted on him.
But then she was roughly shoved into it, and she couldn’t kill them, she just couldn’t, and she finally realized the only other option was to torture it out of them. She figured Aurors like them could take it, right? All they had to do was answer her questions, it wasn’t like they were weak people—they were bloody aurors. But when she saw the light begin to fade from their eyes she turned to Rodolphus and tried to stop him, begging him to let them go because they have a child, for god’s sake let them go.
But he wouldn’t, and he couldn’t let one of them grab their wands so he held Bellatrix by her neck until she kept going for Alice. And when the pair finally cracked, she hated it. She knew exactly what they’d been through and she couldn’t believe that after so many years of trying to fight that curse, she caused people to lose their minds from it.
And when the lights flashed all around her, the brilliant white lights of the aurors, all she could do was look at her scene and cackle.
If she’d’ve ve gone back home that night, perhaps she would’ve made it out sane still. Mentally ill, but functioning. Found a way out of Voldemort, devoted herself to something else, forged a relationship with her sisters again.
But she went to Azkaban. And she lived out fifteen long years dwelling in the fact of what she’d done to so many people, and it made her go mad.
She was in the cell next to Sirius. At first, she tried and tried and begged and pleaded for forgiveness, if only to have her cousin talk to her. But she never even got a reply, and she deserved that, she supposed.
After those fifteen years, she was gone. All traces of the old Bellatrix, the responsible sister who had the ability to feel remorse and regret for her actions—she was gone.
And in the moment she saw Neville, on that fateful day in the department of mysteries, she meant it. It didn’t show through her taunting tone, but a small part of her hoped and prayed they’d made it out okay. But she knew they hadn’t.
And that is how we were stuck with a monster.