Paladins and evil
I wouldn't was to ask your friend to change his character nor do I want to change mine. Perhaps a better option would be for War to receive a direct order, from whichever authority he recognizes, to work with the party for the greater good. That way we'd have the interesting tension between wildly divergent moral outlooks, but hopefully we can all work together to keep things from degenerating into intra-party violence. As long as the lines of communication remain open OOC, things should work out fine IMO.