>>536529326
He has nothing else but the knowledge that adepts are going to destroy everything, as per his father's notes. Plan A was to contain them, plan B was to genocide an entire race of people. Copen is not as evil as he's trying to appear and is clearly not very happy about needing to slaughter millions, as it is all coming from a place of grief, rage, and the burden he has to carry. The Adept Slayer and all the religious larping is not who Copen *is*, but a mask Copen chose to wear to protect himself from the atrocities he was going to commit.
I appreciate that he ultimately threw his family aside. Even though the healthy decision would've been to stay behind and assist his sister, humans don't just tear out sections of their psyche and cleanly replace them with flawless new pieces, we have to take existing pieces and rearrange them into something new. We stay true to our own internal logic, even if that logic is flawed. Copen has for who knows how long sold himself the belief that Adepts will destroy humanity only he can stop this development, and as of the end of GV2 effectively demonized himself. He refuses to stop, because he can't.