hye-sung isn’t a bad person, he has trust/abandonment issues. he abandoned byul because of that, because he had the mindset of how could he stay and be a mother when his own mother didn’t stay for him. And technically he didn’t abandon Byul, he said from the beginning he wasn’t planning on caring for him, or staying with him and Dojin. In fact, the only reason he didn’t get rid of Byul in the first place was because of Dojin. If you’re considering the fact that he left the hospital the “abandonment” well he wasn’t planning on staying first of all, and second of all, he only left so abruptly because he thought Dojin/Heesoo were planning on forcing him to stay when Hyesung had literally already made a whole contract saying that wasn’t going to happen.
another thing, because of those issues he has the reason he’s the more hesitant one in his relationship. idk if all the people hating on Hyesung missed his backstory episode but to sum it up, he went through some traumatic stuff.
tl;dr all of Hyesung’s issues are justifiable in his own way. He makes mistakes and he is no where near perfect but if he was just completely perfect then he wouldn’t be the fun character that he is nor would he be human. in summary, everyone hating on hyesung needs to get rid of their grudge for something that happened so long ago in the comic. what else can he do fix his mistakes? he’s already apologized and he’s with byul being an amazing loving parent. imo hyesung is an entertaining character that is realistic and has a full personality.