You can beat the game with no deaths what so ever...
Not easy but possible.
Finished a game WITH the Trainer and Editor and had Zero Kills, Full Ghost and I tried my best to make the world a better place (didn't poison the elixirs, etc.) One body was found and I can only assume it was one of the three thugs outside of Granny's house saw their friend unconscious as my time-stop wore off for a brief second.
I was hoping for a spectacular new wonderful happy ending, but it was just the normal one (i know there wasn't one besides the low chaos, but I was hoping anyway). However, after the credits rolled I got a kiss from my girlfriend and she called me a Good-Boy... I guess that will have to do.
I try to use sleeping darts as often as possible, but I don't know why it seems to count them as dead a the end of the mission. Sometimes I wracked up 17 kills when most of those had to of been sleeping arrows, it makes no sense to me.
If they fall in water or from a high place they are counted as dead.Found this out in the Sewer choked a guy out did not think he was dead but I choked him when he was close to the water and when I finished I got 1 dead.