The character of the child is the reflection of their parents/guardian. People learn from imitation. That's why good parenting is crucial.
I see that but most people strive to be unlike their parents in hopes not to repeat the same cycle, or they won't engage in anything that could remind them of that trauma AT ALL. I guess it would different, or I would consider it good character development if he tried not to be like his father and ended up mistreating Doc Dan without meaning to. At least then he would become self conscious of his decisions and apologetic, and the flashback would hit harder on some "you're just like you're father" type shit. Bcs even when people try not to be like their parents, sometimes you can't help it, but home boy doesn't seem reflective of his actions at all.
And let's say the coach and the old woman decided to take him in, they should be held to a certain level of accountability for letting him get so bad if they were taking in young students without good role models or supportive households. Like lil boy got jumped on the first day, were those kids not reprimanded. I'll let it slide if Jaekyung pulls a "you're not my real dad!" on the coach and that's how they drifted apart though.
You're telling me he never reminisced about how he was treated during his childhood whenever he was was treating Doc Dan like shit? You would think he would be a bit more conscious about he treated people after growing up like that; this didn't help him but made him look even more selfish and stupid. Someone spin the block on his ass