After a mission or training or whatever, Rumlow is chafing at having to follow orders from Captain America, and also chafing under the weight of his repressed sexual desire for Cap. Luckily, he's got a brainwashed super soldier who's perfect for taking out anger and repression on. He dresses up Bucky in a terrible, cheap Cap outfit, and brutally rapes him, the whole while talking about he knew "Cap" likes it rough, wants Rumlow's dick, isn't such a big tough guy now.

Light feminization okay, Rumlow repressing stray thoughts of having Cap's dick up his ass by upping the brutality of the rape definitely 100% okay, slapping "Cap's" ass, nipple torture, and excessive finger fucking highly encouraged.