Responses
The difference between Dan and Jk was because Dan was raised by his grandmother, and Jk was being abuse by his father
Dan also had loan sharks in life though. We see how the loan sharks treated him.
Jk later has the coach and his mother. He also didn't have to face creepling debt, loan sharks, SA, and what not. It's not a competition but if it was, Dan would win.
Dan experienced almost the same childhood and yet he grew up to be a kind, gentle soul. I feel bad for kid Jaekyung but his adult version still needs to do better, this just isn't enough to redeem his character.