venom has no compassion for carnage. Venom cares only for the innocent, therefore rendering compassion unimportant. Carnage needs weapons to fight (claws, axes, etc), venom is stronger than carnage and would severly injure him in close range. This fight would be more one of symbiotic proportions than pure physical contact. In that aspect, i find that venom would be victorious since he isnt fully bonded with brock. Carnage calls himself "I", venom calls himself "we".
seperated from the symbiote, carnage would die.
hence, my vote goes to venom.