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.
Won 10 battles in the coliseum.
Obtained all "Tools" commands.
Reached level 50 for all party members.
Defeated Kefka and restored peace to the world.
Obtained all magicite.
Reunited with 10 allies.
Defeated 2,000 monsters.
Acquired all "Blitz" commands.
Acquired all "Bushido" commands.
Reunited with 5 allies.
Completed 50% of the Bestiary entries.
Obtained 500,000 gil.
Reunited with 1 ally.
Witnessed the Warring Triad revive and destroy the world.
Obtained 15 pieces of magicite.
Won an item at auction.
Collected treasure from 50% of the chests.
Attended Emperor Gestahl's banquet and brokered peace.
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.
Collected treasure from 10% of the chests.
Obtained 10,000 gil.
Defeated 100 monsters.
Encountered the frozen esper and awakened elsewhere.
Earned all achievements.
Got "Joker's Death" with the "Slot" command.
Learned 20 enemy techniques.
Used the "Leap" command to learn 50 enemy techniques.
Completed 100% of the Bestiary entries.
Collected treasure from 100% of the chests.
Obtained all hidden items.
Traveled to all the map locations.