Maybe he's with Rollins (yes, preferred) and most of their relationship is based on Rumlow being hurt and insulted and tortured. Maybe he feels extremely guilty about being with another man? Anyway, he likes to be hurt, but everything just gets so much better if there's something to be punished for. If he fails a mission, the sex just gets that much hotter when Rollins makes him pay for fucking up, but he also gets in trouble with the higher-ups and that's much less pleasant.

Anyway, he figures it out: being mean to the Asset gets a rise out of his partner, because the other guy has always felt a little guilty about how the Asset is treated, whereas Rumlow (as a Real Man) at least pretends not to give a shit in public. So he starts being intentionally cruel to the Asset-- not all the time, but when it counts-- ridiculous, cruel punishments for tiny infractions or nothing at all, slapping him when he feels like it, telling the tech department he needs an extra long time in the wipe machine this time.

I feel like this failed to articulate the idea in my head, but basically: give me Rumlow using the Asset as a pawn to get aggression from his partner. Give me Rumlow's partner, preferably Rollins, being appropriately furious but also completely aware of what's happening. And also confused, hurt, just-trying-to-be-good-for-his-favorite-handler-ever Winter Soldier.