Guwon is definitely a black flag whether he killed Jinwoo‘s father or not. In the world they live in their relationship will never be healthy and Guwon will always be extremely violent. It doesn’t make him a bad character, just extremely morally grey until we get more information. That’s what makes the story interesting!
Honestly Guwon could had easily killed the dad and definitely has some f*cked background to justify his whacko but I feel like it would be more interesting if Teach killed his dad. Couldn't handle it and got a psych break. It would be interesting to see his moral compass be challenged by the revelation. I dont think how Guwon runs the town is completely fair but will killing him really solve their problems or create worse? I dont the author will kill him off but it would be interesting if they did.

I do think it is the Teach who killed his dad, not Guwon. Or even if Guwon did then his dad wasnt his "dad" anymore. Idk if zombie or whay is going on lmao.