you really hate someone so bad that you lust for 'em, leading to hate sex
two people, rivals in a competition, hate each other so much that they get sexual tension and have hate sex.
Sex that's rough between two people that absolutely hate eachother.
witness 1-"Did you see that Sweden and Denmark? They sure were brutal in bed!"
Screaming fan girl-"Yesh but that hate sex was smexy like DAME!"