[Darth Baras (spoiler)]

There is, and never will be, a use of "one shot" other than killing someone in... one shot. Saying you killed him first try is, well killing him first try. first pull, first whatever. But it is just ridiculous to say you "one shoted" him, when in fact you likely used 30-40 shots. Just think about it for a second, and it will all become clear. ONE SHOT.