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.
Collected treasure from 100% of the chests.
Won 10 battles in the coliseum.
Reached level 50 for all party members.
Learned 20 enemy techniques.
Traveled to all the map locations.
Obtained all magicite.
Obtained all "Tools" commands.
Obtained all hidden items.
Acquired all "Bushido" commands.
Reunited with 10 allies.
Reunited with 5 allies.
Acquired all "Blitz" commands.
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 500,000 gil.
Defeated 2,000 monsters.
Used the "Leap" command to learn 50 enemy techniques.
Got "Joker's Death" with the "Slot" command.
Obtained 15 pieces of magicite.
Won an item at auction.
Defeated 1,000 monsters.
Performed in the opera and obtained the airship.
Encountered Ramuh and obtained his magicite.
Protected the frozen esper and ousted the Imperial troops.
Obtained 100,000 gil.
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.