They're both assholes honestly if you think about it and so the only one that has repeatedly assaulted YW is Seoin, doesn't matter if YW let it slide and Seoin apologized. I don't hate Seoin at all, and I'm not delusional in thinking YW and Taegu should ever be together but I feel people villainize Taegu way too much. It was very much hinted that Teaugu and YW were close before YW reunited with Seoin so it's not "all of a sudden" that Taegu started wanting to be in his space. It was clear from the first chapter that Taegu harbored feelings for YW (which is frankly disgusting considering he knew him since YW was in middle school). I love Seoin but we need to stop acting like his actions are any better. Both Seoin and Taegu are incredibly manipulative. One of the reasons I enjoy reading this is that neither love interest are inherently good people
People saying the truth ain't villianizing. The truth doesn't change just because it hurts you. He's been told to literally mind his own business yet he's in yw business. Seoin has held himself accountable this entire season and that's why he's being given grace. He's apologized for being rapey and rough with yw. He's not shied away from the reality that he's been a piece of shit regardless of his feelings of feeling betrayed being absolutely valid. That is what accountability is, to stop pointing fingers and look within and ask what you have done to contribute to a shitty situation. He doesn't like taegu but respects the place he holds in yw's life. He hasn't gone behind yw's back to remove taegu but what has taegu done? Telling seoin to remove himself and the worst part he is aware of his hypocrisy. Basically wanting seoin to take responsibility for something he never even did and has no idea was done in his name. Is that fair especially when he is aware that's yw's man? We've all read the series and the only reason yw and seoin didn't get together is people getting in the way always. Like let them be. People have caused so much discord between them that it's just tiring when they really like each other.
I still stand by my opinion that some readers are making Taegu's actions so far worse than they actually are. And I see where you're coming from except that half-asssed "apology" Seoin gave cannot be considered taking accountability especially since he waited until AFTER confessing to apologize and didn't even say half stuff he meant to say. But i guess it only gets a pass because YW is too nice and too in love with Seoin to care. Seoin has expressed his dislike of Taegu several times to the point YW is aware. He does not respect him in the slightest. Both hate each other for their involvement in YW's life and neither character's actions so far (in my opinion) has proved better than the others.

I wanted to give taegu grace but Lord this entire season he's been nothing but a nuisance. Even his backstory didn't redeem him. He is literally one of the main reasons yw was getting beaten black and blue. In what world can you ever believe yw deserves to be with someone like that? And so far we've not seen any apology for that shit. Like you are a grown man pining for someone who has made it clear to you they don't want you not only cz they love another but as much as Yw doesn't hold grudges he just doesn't want a person that has ruined countless lives as a partner. I'm so glad for once a series isnt romantising thug romances. I wouldn't want to be with someone like this simply because "they're so nice to me so I see no problem with him fucking up other people's lives."
Yw quitting working for him and not wanting to return was the first sign that he needed to just leave him alone. This father/brother figure bs is not an excuse to be so dismissive of someone's boundaries. Is it because he is older or because of the history that he feels he can't just let yw live his life? Once again I say yw is a grown man and it is in his right to live the life he wants. Taegu not liking seoin don't mean shit.
For arguments sake let me accept taegu is in love with yw, why didn't he make a move until someone that yw likes came along? That's so calculated. That is so weird to me like you had all this time to make a move now when your chances are zero you just want to be a cockblocking agent of Satan? Yeah, no! All of a sudden you want to be in his space all the time. Just leave. If you clock that someone doesn't feel the same way you do leave. Sometimes you'll make them hate you simply because of your unwanted presence. Seoin has every right to tell yw he needs to create distance. Couples have to tell each other stuff when they spot weird shit. Y'all saying he's being manipulative are the people that let outsiders interfere in yalls relationship then wonder why things didn't work out.
Lastly, just because you like someone doesn't mean things have to work out. People have the right to reject a person they don't want regardless of how nice the other person is. No one is owed love that someone doesn't want to give. Read the room accordingly and leave. Taegus relationship with yw is on the chopping block. His little stunt to guilt seoin to leave ain't working in his favour. We all know who's at the top of the priority list for yw and it ain't taegu. Nowhere has yw spoken with so much love that taegus presence kept him going, all that was dedicated to seoin his beloved. Seoin ain't perfect but you can't knock him down for not putting his best foot forward and apologizing and holding himself accountable. All season what has taegu done but make yw uncomfortable with every interaction they have. Even in love there has to be respect for boundaries especially when you've been made aware you are crossing them.