Consensual BDSM is a kink. Kinks are fine, because they are a choice, whether that choice is made by the player (preferrable) or their character (acceptable). Tying someone up and doing things to them without consent is a crime.
So, the main issue with that Maxy scene was not so much the choice of kinks, but trying to sell a love interest that lacks basic respect for your human rights. Of course, something can be wrong and still hot. Just be aware that there is a point of no return, and it's usually reached far sooner for the reader than it is for the author. You managed to keep Maxy's actions in the "wrong, but I'll forgive it this once" zone for me, but that could easily have gone differently.
Now, this is your story. Write whatever you want, art should be free. So, If you want to write a villainous villain doing villainous things, please do. Heck, I can even see a female villain being sexually desirable while being hated as a person. However, actions have consequences. If your villain does damage, that damage will be done, and usually can't be undone.
A word of warning though: Stay consistent. Don't try to redeem inexcusable actions with poor excuses and sob stories. It will only end up destroying your narrative's credibility, and that's what carries the story. Poorly made redemption arcs are on on my personal top ten list of bad writing sins that even fairly decent writers still make too often, with fatal results for the story.
(Columbo voice) Oh, one last thing: Expect to lose 99% of the audience if the scene with Cassandra and the villain turns out to be NTR or similar. It's the one thing you won't ever get away with if it wasn't on the box in big red letters from day one.