What I understand from the "I want to ruin you" line is that Colton did not want jinwoo to be part of an exhibition and then fail and feel like it was his fault. He wanted to put on a solo exhibition and if jinwoo fails it will not be his fault but instead jinwoo would have a reason to blame someone other than himself. He could put the blame on Colton. say Colton ruined it for him by putting on a shitty exhibition or something.
I DON'T KNOW IF THAT MAKES SENSE BUT IT WAS CUTE IN MY HEAD. I want them to have love 80 seasons with them doing nothing but just hanging out. I love these old men!!!!