There is a way to kill Delilah the witch at the very end of "The Surge" mission. This is the last mission in the knife of Dunwall.

I did a full Ghost/No Kill of the level and I saved the game just before the final cinematic. Then I watched the end cinematic and the mission says I didn't kill anything and was never detected. Zero kills at shown in the final level statistics.

So I noticed where the witch spawns on the ledge just above your conversation with Billie Lurk. So I reloaded the save game and placed arc mines right along the wall right there where she will spawn.

Then I begin the end cinematic again. You never see the witch die, however at the end level stats, it now says that Civilians Killed = 1, previously it said 0. This means that the witch/Delilah at the end is considered a civilian and is killed by the arc mines. Too bad the game doesn't give any kind of special credit/achievement for this.

lol nice ^_-

but killing her now would ruin the up comming dlc that gives you that chance

Whoa! Really nice.

It's a pity that this isn't recognised by the game.

Nice find