Steve Yun posted:

It’s the buildup of all the emotional abuse he takes over the whole movie

He endures Mr Park announcing in front of both of his children that he smells bad and has the stench of poverty and he’s unable to defend himself

His home is destroyed with poo poo water and he sleeps in a gym and then is called into work the next morning and has to pretend everything is ok

Driving Mrs Park around while he’s tired, Mrs Park makes it obvious that she thinks he smells bad too

He is uncomfortable with the Indian skit and Mr Park subtly threatens his employment. Even though Mr Park is paying him overtime, Mr Kim feels like he’s been put down. It’s not about the money so much as the abuse he’s forced to endure

When his daughter is mortally wounded Mr Park leaves her behind and literally steps over her body to take his fainted son to the hospital

And finally he pinches his nose at Geunse. Mr Kim getting angry is a little ambiguous here because you can interpret it as 1) Mr Kim getting enraged that he’s looked down on and put in the same category as Geunse, or 2) having a moment of class solidarity and enraged that Mr Park looks down on Geunse