Awespec
As a normal human being, I would certainly feel guilty even if I had to kill someone that was aiming for my life. I just can't be convinced when the protagonist suddenly turns into a cold blooded killer just because the world changed or that someone tried to kill him. Humans adapt, sure, but they do it as time pass and not instantly like trash cultivation MCs.
J_S_2998:Guilt about killing people who would have killed him if he hadn’t killed them? No thanks.
I like this story so far. It has a great intro and would improve greatly if the MC is at least childhood friends with the love interest. The thoughts and personality of the MC is the that of serial killer. To fixate on someone without having any other connection is like the sparkling vampire thing. A very unhealthy relationship.