How to Honorable, Best Ending
Micah and Arthur fight to a draw, and Dutch interrupts Arthur’s attempt to grab a gun and finish Micah off. Arthur talks about how in the end he tried to change and did his best to do so and thus even though he’s dying, he feels like he won.
It is basically a big ol’ slap in the face to how Dutch and Micah both stayed awful people instead of trying to change.
Then, since his tuberculosis is killing him anyway, Micah & Dutch leave to avoid the Pinkertons, leaving Arthur behind to die in peace. Arthur passes away while looking off into the sunset.
The game ends with another Deer sequence that honorable Arthur has seen throughout the game. This time, it’s frolicking all happily.