I watched this drama and the other one ( can't remember the name right now). These are my thoughts. This drama had moments that were very sad, darker, and more serious than the other one. Not going to lie, I shed a few tears in certain scenes. The other one had a mostly lighter tone. I never shed a tear when watching that drama.
This drama had okay fight scenes with the male lead BUT I loved the fight scenes in the other drama. It gave me more satisfaction for the bullied main lead.
I think this ending fits the story. Yeon Chan Young (the 18 yr old who was bullied) was never friends with Jae Yung? Sure he wanted to be friends but Jae Yung had his own problems. So the personality of YCH being friends with JY would have never worked. They were both hiding and weak. JY needed a strong " personality" to teach him how to be strong and to be a good friend.
So leaving the gangster soul in YCH made sense. Like he said he was tired. He has been through a lot in his 18 years. He would never be able to take over the life the gangster already set in motion.