So, the usual kidnapped-by-HYDRA-and-raped Steve thing (go as violent as you want). Steve was a virgin, and while recovering and going through therapy he tries to create positive associations for sex via gentle vanilla stuff (oh Sam, at least you tried) but he realizes he can only get off on really serious shit, like break-the-headboard at an absolute minimum but ideally DP, fisting, etc. Bonus points if only his fellow supersoldier can actually fuck him hard enough to satisfy his need.

(I feel like I've read this kind of stuff with Bucky at the center but tortured!slut!Steve gives me life)