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I've been thinking about it. Among the Orcs, there are two candidates: the Ogre and the Standard Bearer. Actually, I'm not sure if Ogres can speak in full sentences, so among the Orcs, it's more likely the second one – the Standard Bearer.
If we consider the Dwarves, maybe it's the Chieftain; he could have killed again, although, perhaps he was just unlucky. Killing with him is generally effective, but I'm not sure.
The Engineer might be a possibility, but he doesn't seem like an executioner, and not a very ruthless killer. It doesn't quite fit.
The Miner isn't a good fit – after all, a pickaxe doesn't deliver a very impactful blow.
The rest don't fit based on their weapon type.
So, our killer is agile, intelligent, wise, armed with a bludgeoning weapon, and has a collection of "Che" quotes. Among the Orcs, the Standard Bearer fits, and among the Dwarves, I'd go with the Chieftain.
I think it's the Dwarf Chieftain. Of course, if the description is very, very accurate.
Most likely, I'm wrong. Maybe it was the Orcs who did the killing.