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