Full list of all 21 Far Cry Classic achievements worth 400 gamerscore. It takes around 10-12 hours to unlock all of the achievements on Xbox 360.
Complete the game in Hard or Realistic difficulty.
Do not let Valerie die even once in Swamp.
Complete Treehouse without dying.
Complete Volcano Mission.
Kill the Traitor with a melee attack.
Defeat Krieger.
Complete Dam level without equipping a weapon on person (mounted weapons are allowed).
Complete Swamp Mission.
Kill Crowe with a headshot.
Score 1 kill each from a land, maritime and aerial vehicle.
Complete Rebellion Mission.
Complete Steam Mission.
In Bunker, make the Mercs and the caged Trigens mingle with each other
Collect the Key card in Research without alerting anybody!
Fall over 150m and survive.
Complete Pier Mission.
Get a headshot kill from 500m.
Do not die while Doyle hacks the entry gates.
Complete a level with full health and armor.
Complete Training mission.
Run over 5 enemies while driving a vehicle