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.
Collected treasure from 100% of the chests.
Completed 100% of the Bestiary entries.
Learned 20 enemy techniques.
Defeated Kefka and restored peace to the world.
Obtained all magicite.
Got "Joker's Death" with the "Slot" command.
Reached level 50 for all party members.
Acquired all "Blitz" commands.
Traveled to all the map locations.
Obtained all hidden items.
Obtained all "Tools" commands.
Acquired all "Bushido" commands.
Reunited with 10 allies.
Won 10 battles in the coliseum.
Reunited with 5 allies.
Obtained 500,000 gil.
Completed 50% of the Bestiary entries.
Reunited with 1 ally.
Witnessed the Warring Triad revive and destroy the world.
Defeated 2,000 monsters.
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.
Used the "Leap" command to learn 50 enemy techniques.
Defeated 1,000 monsters.
Performed in the opera and obtained the airship.
Encountered Ramuh and obtained his magicite.
Obtained 100,000 gil.
Protected the frozen esper and ousted the Imperial troops.
Completed 10% of the Bestiary entries.
Met with Banon and decided to oppose the Empire.
Defeated 100 monsters.
Collected treasure from 10% of the chests.
Obtained 10,000 gil.
Encountered the frozen esper and awakened elsewhere.