No he's not a good guy. Treating nakyum like nobody because he's bitter is still understandable. But putting stones in someone food cause you're bitter and couldn't sit well with the fact that the other person had it easier than you is straight up bullying and nasty. And then he had the audacity saying that it's a prank. Like bruh??? He was only able to put stones because he doesn't have much power to assert like Seungho. If he does has the power I can assure you he would be as terrible or even worst than Seungho. At least Seungho literally couldn't give a fuck about anything that had nothing of his interest. He don't mess with people unless people mess with things that are related to him.
Never said he was a good guy. Besides, he’s bitter and angry because he doesn’t have power and is facing abusive conditions because he doesn’t have power. We can’t guess what he’d be like if he had power because he’s only really defined by being bitter and an asshole due to not having power.
Also Seungho is pretty bottom of the barrel, as it comes. He’s a homicidal, physically and emotionally abusive rapist. I mean, he literally kills a dude in the first (? Or one of the first) chapters in cold blood because he thinks he gave him the wrong info (which, now knowing Seungho is a clever, manipulative bastard, he obviously knew Namkyun was just lying to him, and killed an innocent man to intimidate him/try to threaten the truth out of him).
Look, I don’t agree with that dude mistreating Nakyum, but I honestly kinda feel for him? I mean, dude is probably worked half to death and works for a psycho (a hot psycho, but a psycho nonetheless). So I mean, dude resents Nakyum since Seungho is untouchable. It’s not right, but it makes sense. Dude is honestly probably a better person than Seungho afawk anyways.