Here is the full list of all 26 Call of Juarez: Gunslinger achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Complete the Story on True West difficulty.
Get all Arcade Mode stars.
Score the maximum of 3 stars in any Arcade mission.
Complete all Arcade missions.
Complete the duel challenge, winning all duels honorably.
Kill a bird during a winning duel.
Complete the Story on hard difficulty.
Forgive your lifetime nemesis.
Collect all Nuggets of Truth.
Unlock all skills in Story Mode.
Fight in Concentration for 15 minutes.
Complete the Story on any difficulty.
Kill your lifetime nemesis honorably in a duel.
Find and kill Jim Reed.
Kill a shotgunner with a close-range shotgun blast.
Shoot a flying stick of dynamite and the one who threw it on a single Concentration.
Unlock both exclusive weapons in a single category of skills in Story Mode.
Reach combo level of 20.
Discover a shipwreck in the Missouri swamps.
Win a duel honorably in under 0.6s.
Find all Nuggets of Truth in a single mission.
Find and kill Johnny Ringo.
Shoot through a hole to kill an enemy that hides behind a shield.
Give it to them straight about your meeting with Pat Garrett.
Kill 5 enemies when falling down through the air.
Unlock a skill.