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.
Kill your lifetime nemesis honorably in a duel.
Unlock all skills in Story Mode.
Collect all Nuggets of Truth.
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.
Kill 5 enemies when falling down through the air.
Shoot through a hole to kill an enemy that hides behind a shield.
Get all Arcade Mode stars.
Complete all Arcade missions.
Fight in Concentration for 15 minutes.
Complete the Story on hard difficulty.
Complete the Story on any difficulty.
Forgive your lifetime nemesis.
Find and kill Jim Reed.
Complete the duel challenge, winning all duels honorably.
Discover a shipwreck in the Missouri swamps.
Score the maximum of 3 stars in any Arcade mission.
Kill a bird during a winning duel.
Win a duel honorably in under 0.6s.
Reach combo level of 20.
Unlock both exclusive weapons in a single category of skills in Story Mode.
Find all Nuggets of Truth in a single mission.
Find and kill Johnny Ringo.
Give it to them straight about your meeting with Pat Garrett.
Unlock a skill.