Well, sir, you are a cowardly son of a bitch! You just shot an unarmed man.
6 seconds sound clip from the Unforgiven movie soundboard.
You can hear this line at 01:56:07.027 in the Blu-ray version of the movie.
Quote context
[...]
- I own this establishment. Bought it from Greely for $1000.
- You better clear out of there.
- Just hold it right there. Hold it!
- Well, sir, you are a cowardly son of a bitch! You just shot an unarmed man.
- Well, he should have armed himself if he's going to decorate his saloon with my friend.
- You'd be William Munny out of Missouri. Killer of women and children.
- And I'm here to kill you, Little Bill. For what you did to Ned.
[...]