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.
Earned all achievements.
Collected treasure from 100% of the chests.
Completed 100% of the Bestiary entries.
Defeated Chaos and restored peace to the world.
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.
Collected treasure from 50% of the chests.
Reached level 50 for all party members.
Restored the Fire Crystal's light.
Completed 50% of the Bestiary entries.
Restored the Earth Crystal's light.
Defeated 500 monsters.
Collected treasure from 10% of the chests.
Obtained 100,000 gil.
Defeated 300 monsters.
Obtained 50,000 gil.
Played the 15 Puzzle game.
Obtained 10,000 gil.
Completed 10% of the Bestiary entries.
Saved Princess Sarah by defeating Garland.
Defeated 100 monsters.