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