Kylo is secretly needy and affection starved and goes to mush whenever it seems like someone is trying to take care of him in some way. Asking if he's alright after a stressful situation, tending to his injuries, even something as simple as reaching out to straighten a piece of his clothing if its out of place. The person can be as prickly and angry as they want while doing these things, it doesn't matter to Kylo.

This extends to sex too. If someone whispers in his ear that they'll take care of him and make him feel good, he goes to jelly and lets them do whatever they want to him.

Someone figures this out and works with it.