Zero!

teacher is not the accurate term... Torturer of innocent souls is a little closer

Officially she was a teacher.... And not an effective one. Yes, unofficially she was a torturer, and that is closer to reality indeed. :)

She was super competent, her whole point of teaching at Hogwarts was to stifle oppression, and she did that so well, Harry needed to find a F**KING MAGIC ROOM to defeat her

Yeah, if you put it into that perspective yeah... But when it comes to competence as a teacher.... No...
(Ironically, Barthy Crouch Jr. was very effective as a teacher. Even though he was a death eater, Harry learned a lot of important lessons, he needed to defeat Voldemort, from him).

True

We all know one thing, y'all can't escape Umbridge's classes even if you did make a runner for it.

Getting expelled on purpose... maybe?

It could work, but-

BITE MY SHINY METAL ASS