First Visions thread and it's not one of the over-the-top twins?
Though I suppose that's understandable considering they can somewhat throw around literal planet destroying energy. Not really anyone who can challenge them. Nyax who? Gigadrain what?
As for this thread, it depends how powerful those Sith in the Ninth Jedi were. Personally, I see little reason to assume they are inferior to your average Inquisitor. And the leader of them was even capable of using force lightning, a rather advanced dark side technique. I'm inclined to say, the Margrave carves the Seventh Sister up with ease.