I'd have to say lawful evil covers Malacath. Dude seems to be all about his code and honor...Orcish, skull-shattering honor.
He's about as dickish as any of the daedra, too. Fail him, and he'll ruin you and anyone around you until it's fixed. Impress him, and he'll shower you with gifts and power... and then you'll likely die in his service. But, hey, at least that way he won't screw over everyone you know and torture your soul for all eternity.