At the end of the day Doomguy/Doomslayer is humanity's protector and no one else. so I think he will definitely kill the demonlord(Because she is destroying one half of humanity to force the other half to have sex with Mamono.) and the chief god(Because the original one created the monsters to kill humanity in a never ending cycle, the same cycle that the current one is trying to restore) as well as most of the more violent Mamono. The Mamono that get the pass by the order he to will probably let slide as well as most of the gods that don't actively harm humanity. It wont be a total gynecide but heads will definitely role.