Just mouseover all of the corpses (both the ones you unalive and the ones already dead at the time of your arrival to the scene). As long as they show 0/XXXX hp remaining, you're good. If any of them show >0, throw them off a cliff, AOE damage them (doesn't always work), or put them in your camp storage box and leave them there.
If anything 'spazzes' out with odd animations during the fight, triple check those as well. These corpses are registered as 'dead' by the game so they won't show red dots anymore on the minimap, don't use that as a gauge. Physically check each one.
