Joel Miller and William Munny are very similar characters in what makes them who they are. Both have experienced a tragic loss which distills into a kind of moral permission to be cheered on through morally gray violence. Both have violent pasts that have darkened their souls so deeply that even beyond human norms they may be irreconcilable with any metaphysical sense of forgiveness. Both have third acts that show them either saving the defenseless and delivering as much a sense of justice such a bleak world could expect, or only further sealing their morally condemned fate to satisfy selfish desires for redemption or vengeance, at any cost.

Personally, the muddy morality of the lead characters is IMHO what made Unforgiven one of the best westerns/films of all time and made The Last Of Us such a hit video game/show.

Did Will Munny's violent past that included killing women and children to rob a train make him irredeemable? Did the lives that were impacted and destroyed by the final "lucky" reckoning in the saloon matter less than the lives of his children, or Ned?

Did Joel Miller's talent at killing for his family, for those closest to him make him a "bad" wolf in a world of wolves?

I personally prefer characters that force an internal reflection on why we cheer for them, why we accept or maybe desire a degree of darkness as a necessary part of the narrative metamorphosis to light. Maybe since we know in our gut it never gets as bright as we hope it does, and it can't to be believed when compared to reality.

See Also: HBO's Barry