Here is the full list of all 24 FINAL FANTASY achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Defeated Chaos and restored peace to the world.
Played the 15 Puzzle game.
Reached level 50 for all party members.
Collected treasure from 100% of the chests.
Obtained Excalibur.
Restored the Wind Crystal's light.
Traveled to all the map locations.
Restored the Water Crystal's light.
Gained titles of courage from Bahamut.
Completed 50% of the Bestiary entries.
Collected treasure from 50% of the chests.
Restored the Fire Crystal's light.
Restored the Earth Crystal's light.
Obtained 100,000 gil.
Obtained 50,000 gil.
Collected treasure from 10% of the chests.
Defeated 500 monsters.
Defeated 300 monsters.
Obtained 10,000 gil.
Defeated 100 monsters.
Completed 10% of the Bestiary entries.
Saved Princess Sarah by defeating Garland.
Earned all achievements.
Completed 100% of the Bestiary entries.