I had planned on slipping one of them a powerful home-brew frenzy potion, but actually they got themselves neatly killed for me.
I was on a radiant quest for the Companions to take out an escaped criminal in Markarth. When I arrived, I saw the tell-tale pointer was down near the smelter. There he was, walking up the slope towards the inn. I spoke to him but didn't use the dialog option to challenge him. Instead, he turned and attacked one of the smelter workers. This triggered all the guards to attack, including, to my surprise, the two Thalmor soldiers. Normally they are pretty tough, but I suspect that the spawned villain was level 50ish. Two or three hits and they were dead. I just stood there and watched the mayhem.

In the end the villain was dead, along with the smelter workers, the two Thalmor, and maybe half a dozen guards. If it were possible, my character would have brushed imaginary dust from his hands while saying to nobody in particular, "Well, my work here is done!"
