I will echo your sentiment about Unforgiven.Absolutely agree! However...
UNFORGIVEN is probably in the top three of my favorite Westerns and I know I'm not alone in that regard. I think the thing that sets the movie apart is how killing weighs on the main characters. The scene with Will, Ned, and the Kid ambushing the cowboys revealed a softening of the two hardened killers. Will's wife is credited with reforming him throughout the movie. We don't get as much background on Ned but he is adamant that "We ain't bad men no more" early on.
When the Kid killed Quick Mike the crushing reality of what he had done shocked him to the core causing him to abandon his aspirations of being a "villain" as Little Bill would say.
Not technically a gunfight scene but in the opening of DANCES WITH WOLVES, rather than allow the battlefield doctors to amputate his leg Lt. Dunbar attempts suicide in spectacular fashion. If somehow you have missed either of these great movies they really are must see
The entire theme is that some men can kill in cold blood and most of us can't. How hard it is for a normal conscientious human being to take the life of another human being. How most of us recognize how evil and final that act is, and how thoroughly it violates the Golden Rule.
The movie gets into, what is it about some people that they can kill with impunity. Even if their conscience later bothers them and they drink to forget, they can still do the unthinkable that most of can't.
My favorite scene is the jail scene where the Sheriff teases the writer to shoot him so English Bob can escape. "Hard ain't it?" But yes, amazing movie. My #1 favorite Western.