Tamaki/Kyouya. Kyouya gets off on pain, and enlists Tamaki's help to that end. And I'm not talking about giggly nipple-clamps or cock and ball torture; I mean kicks and punches, cuts and bruises, the whole nine yards.
Up to you on how to address the issue of concealing the injuries, if at all. Also up to you is whether Kyouya reciprocates.