Umbran said:
Yeah, well, a high-level assassin doesn't go down to a couple kicks to the head in D&D. Even a high level mage doesn't. Too many hit points. Either the assassin wasn't as threatening as you thought, or you got the wrong guy. Anything that falls to a couple shots from a boot isnt "the most lethal thing he came across".
On the other hand, it sounds like the DM was only allowing him to use the D&D-accepted nonlethal damage rules to knock the guy out. Maybe there was miscommunication, but it sounds like they pin the guy, stated the intention to knock the guy unconscious, and the DM said, "yeah, but you have to use uanrmed attacks to do it." At which point the two PC's decided to go about it. Had the DM allowed say a nonlethal Coup de Grace on this pinned and effectively helpless opponent, it might have "looked" cleaner.
From a DM's perspective, it looks like the guy went down in two rounds for one of two valid reasons:
--They pinched a low-level would-be assassin, instead of the real deal (a guy who throws poisonous vermin at me counts as an attempted assassin, I'm sorry to say).
--They pinched the Big Guy, and the DM saw his NPC getting hammered after two rounds, couldn't get free from the other PC's death-grip, saw the writing on the wall, and said, "OK, he goes unconscious", not willing to play out this nasty little scene any further.
Without the DM, I can't say with certainty. Occam's Razor suggests the first one, but the second scenario is not improbable.