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