I hope he actually betrays him. we can see Lee go further and further off the deep end and Chief Baek is just now acknowledging how far he's going. What if in the future Lee goes for the innocent just because they had a passing relationship with the people who drove his daughter to death? Or what if instead of killing them he ruins their lives and lays the evidence on the bullies? It would go towards his revenge plan but he would slowly snowball from the bullet he is now into a tactical nuke that would destroy everything in the general area of his target. We could see Chief Baek slowly become an antagonist and instead of letting Lee kill himself or something he makes him face justice for what he does because he knows that every moment he will spend alive after everything is over will be nothing but agony to Lee.
But for me, chief baek can't be traitor because lack of motivation, and he doesn't look cunning, like aizen and gin relation, we can see how gin always some kind of mind or plan for aizen but chief baek more like respect
chief baek sacrificed at the end I can see that when they fight last bullies families that has higher influences