Ok, so we know both of them are bad but who is really the more evil villain, Umbridge or Bellatrix?
Here is my opinion...
Dolores Umbridge is more evil because the things she does are more likely to happen in our lives. I am sure we will all have or had that one person/ teacher in our life.
Bellatrix Lestrange really just does her evil deeds because she is obsessed with Voldemort. If Tom Riddle had never been in her life, things might change and we probably wouldn’t be hearing THAT laugh very often.
So that’s what I think, what is you POV?