Oh man, that's a nightmare set of talents.
I'd try and set him up in a duel with another warlord, see if you can get someone to do your dirty work for you. Otherwise, run away a lot and try to kite him near fire.
From a reddit thread about a similar issue:
"First, you need to get the ignite perk. Its first tier, so if your low level killing a couple grunts and some chump captain should get you the necessary exp. Next, you'll need to plan your fight. Bring it to him this time. If he's in a fortress great, just stalk him a bit till he walks by a barrel then blow him up. It won't kill him, but he'll panic and run. Ignore everything else and chase him. When you get close, grab him, then start shanking him. Or you could just use him as a Orc shield while his grunts attack you, it won't matter if he's got combat master if other orcs attack him. If he's not in a fortress and just on patrol, it might be worthwhile to let him kill you a few more times so he becomes a bodyguard or war chief."