Can't paladin be a traitor? He has 0 kills but that don't make him innocent. With lie detector and peerless reputation he can be manipulator type villain.
Why not just ask them to let him kill them? Tell them his skill. They still be alive after reset.
They have lie detector and if they denied his request mc can just kill himself to keep his secret.
And for Sword Saint questions he can say that he killed people with their permission.