Luther is a very independent individual. He definitely prefers keeping to himself and likes to be able to fend for himself. He doesn't believe that their are any good people in the world and thus trusts nobody.

He's not the merciless sort, he recognizes that killing or harming just to do harm is wrong. He merely kills for survival, nothing more, though, he is very strong and thus can injure without ever meaning to. Luther sees in infrared. That being said, he sees heat signatures, and thus can see where anything living is as well as seeing when someone is injured or ill. He's not likely to help you if he sees your body is weak, but he's also most unlikely to hurt you because you are weak.