This trope is a personal peeve of mine. Guy is in a relationship with a woman, or has declared his love for and is courting a woman, then he's caught being unfaithful. The woman is understandably angry because of his insincerity, but what's his reaction? He bloats with pride, shows a big shit-eating grin, and goes: "Hahaha you really love me, huh? You're crazy for me, huh? That's why you're batshit jelly right now, huh? Admit it, you can't stand other women around me and you're hopping with jealousy 'cause you love me so terribly! God, I'm such a WINNER!" No remorse, no guilt, no shame, he's just pleased with himself and happy that he hurt her. I dunno why some writers think this how a cool lead reacts in that kind of situation. I find it gross and infuriating.
And it looks like in fact the trope is not limited to male characters. You can make a female seductress rotten and conceited like that, and it's just as gross and disgusting.