Here is the full list of all 36 FINAL FANTASY VII achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Complete FINAL FANTASY VII
Defeat the Ruby Weapon
Reach level 99 with any character
Get Cid's last Limit Break
Master all Materias
Defeat the Emerald Weapon
99,999,999 Gil
Get Cloud's last Limit Break
Defeat the Ultimate Weapon
Complete the second part of the game
Defeat the Diamond Weapon
Get materia Bahamut Zero
Get materia Knights of the Round
Get a Gold Chocobo
Get Vincent's last Limit Break
Get Tifa's last Limit Break
Get Barret's last Limit Break
Reach the maximum level of any Materia
Complete the first part of the game
Get Yuffie's last Limit Break
Use Cid's 1st limit
Get Aeris's last Limit Break
Get Red XIII's last Limit Break
Use Vincent's 1st limit
Get Vincent on your team
Get Cait Sith's last Limit Break
Start a battle in the Battle Square
Use Cait Sith's 1st limit
Use Yuffie’s 1st limit
Get Yuffie on your team
Use Red XIII's 1st limit
Use Aeris's 1st limit
Use Tifa's 1st limit
Use Cloud's 1st limit
Use Barret's 1st limit
Win your first battle