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