Im surprised at how not much people have picked up on this, but it's obvious that the mc pain kink or BDSM is a trauma response. He only feels love when he's being hurt by other people because that's how he was brought up. Mind you he had absolutely no parents and his guardian basically left him with basic necessities for surviveal. He was never allowed to build relationships with other people and being involved in a gang all he probably knew was violence, hence where he would develop a pain king as a trauma response.