Here is the full list of all 37 FINAL FANTASY VI achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Earned all achievements.
Defeated Kefka and restored peace to the world.
Completed 100% of the Bestiary entries.
Obtained all magicite.
Collected treasure from 100% of the chests.
Obtained all "Tools" commands.
Traveled to all the map locations.
Obtained all hidden items.
Won 10 battles in the coliseum.
Reunited with 10 allies.
Acquired all "Bushido" commands.
Learned 20 enemy techniques.
Got "Joker's Death" with the "Slot" command.
Reunited with 5 allies.
Acquired all "Blitz" commands.
Reached level 50 for all party members.
Completed 50% of the Bestiary entries.
Reunited with 1 ally.
Witnessed the Warring Triad revive and destroy the world.
Collected treasure from 50% of the chests.
Attended Emperor Gestahl's banquet and brokered peace.
Obtained 15 pieces of magicite.
Won an item at auction.
Obtained 500,000 gil.
Performed in the opera and obtained the airship.
Defeated 2,000 monsters.
Defeated 1,000 monsters.
Encountered Ramuh and obtained his magicite.
Obtained 100,000 gil.
Protected the frozen esper and ousted the Imperial troops.
Used the "Leap" command to learn 50 enemy techniques.
Completed 10% of the Bestiary entries.
Collected treasure from 10% of the chests.
Met with Banon and decided to oppose the Empire.
Obtained 10,000 gil.
Defeated 100 monsters.
Encountered the frozen esper and awakened elsewhere.