How many of you could actually take a life??

To properly answer your question I would need more info.

example 1. If you are in the military and say working on ordnance and you do your job well and that "bomb" does its job and destroys the building and occupants inside, then you have indirectly taken lives.
example 2. If you are dealing with a robbery and the individual starts to bring the gun up to a family members head and you shot and kill the robber, then you have taken a life in self defense.
example 3. If you are drunk and full of gusto and the stupidity is flowing strong and you decide to shoot up the bar and kill people, then you have taken needless lives in cold blood.

So to answer your question, the circumstances will greatly effect each persons answer depending on the situation.