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