As much as I love all of them, and again you can add any other characters from different games that are gunslingers, I vote for Red Harlow.

Jack in the epilogue was on the same level as rdr1 John who was better than Arthur despite only being 19 so I voted Jack

@Osborne124 true that Jack is on the same level as John

To be honest I don’t think John or Jack ever became a better shot then Arthur while John is my favorite character I just think Arthur was the best shot. As for Red or Cole while they were good ( and you can just chalk this up to game mechanics) they don’t seem as smooth or casual about their draws as with Arthur is looks more like reflex the actually trying

@JC Carbone true. Don't forget Nisha with her marksmanship abilities in Borderlands: The Pre-Sequel