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.
Get all Arcade Mode stars.
Complete the duel challenge, winning all duels honorably.
Complete all Arcade missions.
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.
Complete the Story on True West difficulty.
Collect all Nuggets of Truth.
Unlock all skills in Story Mode.
Complete the Story on hard difficulty.
Kill your lifetime nemesis honorably in a duel.
Fight in Concentration for 15 minutes.
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.
Complete the Story on any difficulty.
Forgive your lifetime nemesis.
Find and kill Jim Reed.
Reach combo level of 20.
Discover a shipwreck in the Missouri swamps.
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.
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.