In the majority of cases, why waste the ammunition?
It depends on the situation. One-on-one to me is personal and I like the extra touch as I have a rather savage and vicious disposition when threatened or attacked. One-on-many is where one shot to the thoracic triangle shall suffice and where every shot must count.
I can’t speak for Mr. Vader, but personally, if a rapist is trying to attack me, wasting ammunition will be the least of my worries. The reality is I’m more likely to shoot until he stops moving, without stopping to see if he dies from the first shot.
Firing in an immediate, life-threatening situation, is seldom calm and detached. However much I would like to think otherwise.