Why didn’t Sangwoo

A thing that really irks me is to why Sangwoo decides to kill himself instead of Gi-Hun in the finale. When Sangwoo says “I’m sorry” to Gi-Hun, I seriously thought for a second that he’s gonna knife his friend but instead he offs himself.Sangwoo is the kind of a player to take advantage of even the slightest of errors. So I found it quite odd when he didn’t kill his friend. Some people might argue that he’s had a change of heart or he didn’t wanna do it since Gi-Hun was his childhood friend. But I refuse to believe that since Sangwoo had already been through hell. One more kill wouldn’t change him. I’d love to hear the fandom’s thoughts on this