Here is the full list of all 26 Call of Juarez: Gunslinger achievements worth 400 gamerscore.
Kill 5 enemies when falling down through the air.
Collect all Nuggets of Truth.
Forgive your lifetime nemesis.
Reach combo level of 20.
Kill a shotgunner with a close-range shotgun blast.
Complete the Story on any difficulty.
Complete the Story on hard difficulty.
Kill your lifetime nemesis honorably in a duel.
Find and kill Jim Reed.
Unlock both exclusive weapons in a single category of skills in Story Mode.
Discover a shipwreck in the Missouri swamps.
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.
Complete all Arcade missions.
Score the maximum of 3 stars in any Arcade mission.
Get all Arcade Mode stars.
Unlock all skills in Story Mode.
Complete the duel challenge, winning all duels honorably.
Complete the Story on True West difficulty.
Kill a bird during a winning duel.
Fight in Concentration for 15 minutes.
Shoot a flying stick of dynamite and the one who threw it on a single Concentration.
Win a duel honorably in under 0.6s.