I think she was abused. Maybe she had a muggle friend and her parents crucio'd her until she learned that 'muggles are filth'. Yup I'm pretty sure her father abused her.

I think she had a rough childhood kinda like Azula from Avatar the Last Airbender. Maybe she felt pressured by her parents or something.

She was raised in a family that rewarded behavior consistent with the dark arts. It's as easy as that - her "rough childhood" didn't make her "turn bad" - her family taught her that mudbloods are bad and other such beliefs. She followed and her family and other members of the dark community supported her.

Who knows, maybe she really is just evil down to the core - but we would only be able to tell if she had been adopted at birth and raised by a family like the Weasleys. Would she have still turned to the dark side or would she have been against Voldemort?

All in all, it seems to me that she and Malfoy and many other followers of Voldemort are the product of their family surroundings and history.

@Kataang I ♥ Azula!!

Idk why?? But she just is

azkaban and her rewards

Azkaban. And she was raised in a way to hate muggles and muggle borns. Or maybe she was just evil from the core. But people mostly aren't like that from the start. She must have been influenced by people around her like her family, who also believed that muggle borns were bad.

I think it was just genetics. It was a result of all the inbreeding.

loving a man who have no love is hard *nods*

^ that could be it too.

Azkaban and probably that Voldemort didn't seem to reciprocate her feelings

i guess:) or she just wanted to be diffrent and evil. LOVE HER♥

I'm assuming Azkaban pushed her over the edge...Before that though, she probably was a little strange but not as bad as she was after Azkaban

^ I agree with Ms_Mea I think Azkaban pushed her over the edge along with loving Voldemort who never returned the love.

She was raised to believe the Black family was special, superior to all others in the wizarding world. Aslo Azkaban could have took effect to her mind like it had done to many others.

She must have learned it from her parents ;)

Azkaban!

A think thats its because she (like her master) never knew the true meaning of love. Maybe because her sister got all of the glory. I also think that she is a sadist. And the fact that she has been imprisioned in azkaban for so long that it twisted her slightly

Azkaban. And she wanted power and believed that voldemort could give her that.

Azkaban sent sent her crazy, and the Pureblood thing I think her parents drilled into her.

She's creepy...... not much of a reason but it gets explained better in the other comments.

She probably never got her pink my little pony and was raped and molested by her sicko uncle

You think poor Bella was raped!?

Normally a rough childhood factors into a poor adulthood.

you could say she was raised that way, but so were Narcissa and even Andromeda... I guess it's because her role model is Voldemort. Still, if she worships him in the first place, there's something wrong with her

Because she was best friends with a muggle-born, and her parents crucio'd her for that. Plus, they beat her because she stood up for her kind little sisters, Narcissa and Andromeda. Oh,and Azkaban & the fact that she loved the Dark Lord but he didn't love her back.

Es gibt bei ihr mehrere Gründe. Zum einen ist vielleicht schon ihr Grundcharakter böse und saditisch. Sie wurde rassistisch erzogen, sie wurde aber noch böser, als es von ihren Eltern und Schwestern erwartet wurde. Ihre Schwester Andromeda wurde sogar gut und Narzissa änderte sich, wollte keinen Mord, aber rassistisch blieb sie. Draco verlor sogar seinen Rassismus, wurde sogar gut und Regulus ebenfalls, Regulus wurde deshalb umgebracht oder Selbstmord. Bellatrix mordete sogar und folterte und fand das auch noch gut. Einer der Gründe ist natürlich, das sie Voldemort liebte, das sie noch böser machte. Aber wahrscheinlich machte das ihr auch noch Spaß. Ich glaube, sie wollte böse sein und böse bleiben, bis zu ihrem Tod. Wenn sie Voldemort nicht geliebt hätte, ist nicht unbedingt klar, das sie dann so böse und sadistisch geworden ist. Es ist nicht klar, ob sie durch sich und ihre Eltern böse und sadistisch in dem Maße wurde oder ob ihr Grundcharakter schon böse war oder ob sie so böse nur die Liebe zu Voldemort wurde, aber eine große Rolle spielt Voldemort garantiert daran, da er sie zu der Erlernung der Flüche unterrichtet hat, wie sie Harry selber sagte.

@Brooklyn I can see that.

I think it was a mix of upbringing and genetics/her natural mindset and personality. And Azkaban didn't help.