Ren & Hux end up in some seedy backwater bar (because mission) & a bar fight breaks out. In between flinging bodies around & running people through with his saber, Kylo realises that Hux is fighting too, and more importantly, winning. He's also surprised by just how dirty of a fighter Hux is.

Afterwards, while Kylo is standing around flabbergasted and turned on, Hux is calmly holding back a bloody nose while helping to clean up.

+++++ if Hux throws the first punch because someone says something rude about Kylo ("nice hair, pretty boy. Do you let him brush it?")