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