Obviously
Good Girl Gone Bad - if you're like me, you'll have to let the artstyle grow on you, but the kicker is, it's a girlfriend protagonist and there is both a lovie-dovie and a brutal NTR route (even though it doesn't have the NTR tag officially), along with a myriad of other routes.
Well, the actual NTR route isn't so brutal, I guess, but you can dump your boyfriend during a videochat where you let another guy screw you, that's pretty brutal in my book.