wait I didnt get it. why did Ban phuong leave the gang right there and also end up killing the gal ki's eastern chief? didnt that guy gave him like a job at least as he was on the run from killing those 3 rapists of his GF? why bite the hand that fed him?
Ban Phuong may have won the physical fight, but Ken dealt him an emotional blow with one sentence. 'Forget your dumbass ontological struggle between dehumanization and purpose, you failed the basics: helping someone in need.'
Ban Phuong has been on autopilot since he learned the woman he loved died, and that callout just woke him up. He spent hours, days around dudes like the rapists that led his lover to kill herself, and he did nothing. He spent all that time getting insulted and bullied just because of his identity, and he did nothing, even if his father taught what lies at the extreme end of that dynamic (the point of the flashback of Koreans joining the awful Vietnam war with all its war crimes on civilians just for a paycheck).
Since he achieved his vengeance quickly, he didn't do much after it aside running away. Vengeance is a hollow reward, it had to be done but what someone like him would really want is to have been there in time to save his girl. That's a rightful use of strength. If he had helped Miss Yoo, he would have started to heal somewhat by doing what he hoped he or someone would have done for his woman.
That's why he says at the end that they're not likeminded: he doesn't measure up to Ken yet. And he failed 'the test' to join the gang (and he didn't apologize immediately!). And that's why he went to kill the leader of a gang doing things like this, to use his strength to protect people, or at least hurt those that do harm.