And even then she was serving to protect the whole of troll society from the vast glub, as well as feed her lusus, so it's not like she's entirely unjustified.
Protecting the world from the Vast Glub? Oh come on. She built Eridan a doomsday device. She's
completely okay with having to kill people all the time. She'd probably like it better if everyone didn't hate her and karma wasn't always biting her arms off, but the killing part doesn't bother her in the slightest.
And you know what? If Vriska was genuinely a broken and troubled individual who was stuck in an impossible situation because of that, long since past the Despair Event Horizon, I might have her higher up on my troll list.
However, she enjoys it fully. Don't get me wrong, I like a well-done evil character, but Vriska isn't done well at all. Instead of provoking awe or even comedy at the audaciousness of her actions, Vriska is just sickening.
And you know what? SHE'S NOT EVEN A VILLAIN. She's on the same side as the other trolls, working together with them to win Sgrub. She seems to have stopped killing and crippling her friends, and the only strangers left to kill are the four human kids and the residents of Derse and Prospit. She killed hundreds of people and GOT AWAY WITH IT.
Troll society is generally more relaxed about that sort of thing. The closest thing Alternia has to law enforcement are the Imperial Drones, who mercilessly kill those who don't fill the romance requirements. The other trolls didn't really make that big a deal about her killing other trolls. Lying about not killing other trolls, and killing and crippling her friends were the things that cemented her huge bitch status. And from what I gather from her pesterlogs with Equius, even that is pretty much business as usual for the blue bloods.
Addendum:
I read the bit with Troll Andrew again and found this.
No, this is MY LIFE we're talking about here. Bullies. Wolves. Musty attics. Huge spiders. Did I mention the spiders? Let me tell you, I got HELLA spiders up in this...
FORESHADOWING! IT WAS VRISKA'S ATTIC ALL ALONG!