I think Sihyeon (the boss) needs a bigger shock than just Dajeong leaving him, to make him realise how serious his actions are affecting the people he cares about. Because he definitely does care now, more than he did before at least. Maybe if Dajeong also found himself in a life-threatening situation which wasn't cause by his hands would be a big shock causing a change... Though he's pretty unpredictable and I wouldn't be able to tell the outcome for that.
This is the Boss where talking about here. It'll take a lot for him to change. Welp... Either that, either he'll manage to brainwash Dajeong and turn him into Hyeok.
I think Sihyeon (the boss) needs a bigger shock than just Dajeong leaving him, to make him realise how serious his actions are affecting the people he cares about. Because he definitely does care now, more than he did before at least. Maybe if Dajeong also found himself in a life-threatening situation which wasn't cause by his hands would be a big shock causing a change... Though he's pretty unpredictable and I wouldn't be able to tell the outcome for that.