He's acting like he was the victim, as if he wasn't the one who made a mess of things. It's not even a regret arc, it's just a pity party for himself. "Poor me, the dude I manipulated ended up rejecting me...."
The backstory came out of nowhere and doesn't even fit his character, it's so blantantly created so that the readers would empathize with mokyeon. It wouldn't have been so bad if she had introduced it slowly, but no, season 2 had to open with a whole dump of mokyeon's lore just to justify whatever he's done.
The execution is just so poorly done, I find myself hating mokyeon even more.

look i’m usually someone who enjoys it when the seme is suffering so much from regret like i loveeee it when they cry and beg and lose their shit but isn’t mokyeon overreacting a bit here? i get it he has a troubled past but it’s only been like what? a few months? and most of those times they just spent fucking. this type of reaction just seems unwarranted and dramatic for no reason lol lowkey i feel like this manhwa has pacing problems