In my opinion it was Dutch. He has the fastest horse, although he’s the leader it would make sense he doesn’t get his hands dirty as much but he should be leading by example with such a small crew, and what cemented it for me was in the end with the shootout as John with Micah. He knew he wasn’t able to get out alive unless he shot micah, rather than protect the man he’d been running with for years he just shot him and walked away.
Also with Arthur’s ending, I get Dutch walking away from Arthur after going for the money, but the ending on the cliff, he really should of defended his dying old friend regardless of events in chapter 6. Plus he let himself get too easily swayed by the rat. And in the end still ended up carrying on with Micah, even though it’s implied he believed Arthur as he would of just left with Micah at that point.
Also when he’s faced by Arthur explaining Micah was the rat he just went with the strongest, being Micah, even after he killed grimshaw. How could he let that happen, he literally just took the easy way out and ran with Micah!
And has killed innocent women on more than one occasion. In the first game used one as a human shield when confronted by John.