The “Settling Feuds” achievement is earned by completing the third chapter of the game, which spans across two different feuds. The first involves fighting between the Braithwaites and Gray families, ultimately ending in the slaughtering of the Braithwaites, while the second feud is between Dutch and Colm O’Driscoll, which ends with Lenny assisting you in clearing out Shady Belle, and once you set up camp there, you’ll earn “Settling Feuds.”