From EA only perspective, I am confused by others responses here. We have 5 companion options and I don't think I'd describe any of them as evil.
Laezel definitely acts in ways I would say is evil. She flat out tortures an innocent tiefling for information. She will also try to kill you if you dont want to help her out of the cage.
Not really 'good' behavior.
Astarion assaulting you while you sleep isn't exactly good guy material either.
But we all have different lines we draw between what we find acceptable behavior, and that's just my experience.
