Aside from the fact that I as a reader will support Youngguk regardless, the portrayal of the other actor of the villain, despite the nasty taunting with Youngguk, is quite good. It looks good because it's generally agreed upon in dramas and (maybe) in Korean society. When you think of seocnd-generation chaebol (portrayed in films) you almost immediately feel annoyed and the performance transmitted exactly that.
But his performance lacks depth - it didn't separate his CEO villainy character from others. If this guy casted for a common rich son , he would probably get the role, but this role is no common rich son. It is the antagonist, one of the main characters. And as a main character, you cannot have just one "face"/characteristic - for example arrogance. You have to show more, to the point that the audience can sympathize with you. Or be curious to your other hidden "faces".
Back to the scene that the guy has performed, he has shown all of his "face". It's a good performance. But a better performer would not show all his cards. A more intelligent actor would always hold back some parts of his "face" to make audience crave more. So in this scene where the antagonist reacts before threats, perhaps a calmer, more collected reaction would be much preferable. Maybe throwing in some scheming, calculating expression. Be evil AND charming, so audiences have love-hate feelings towards you. At least that's what I see from recent treatric trend.