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
Complete the second part of the game
Master all Materias
Defeat the Ruby Weapon
Defeat the Ultimate Weapon
Defeat the Diamond Weapon
Defeat the Emerald Weapon
Get materia Bahamut Zero
Get materia Knights of the Round
Use Cait Sith's 1st limit
Complete the first part of the game
Start a battle in the Battle Square
Use Cid's 1st limit
Use Vincent's 1st limit
Get Vincent's last Limit Break
Get Vincent on your team
Use Yuffie’s 1st limit
Get Yuffie on your team
Reach the maximum level of any Materia
Use Red XIII's 1st limit
Use Barret's 1st limit
Use Tifa's 1st limit
Use Cloud's 1st limit
Use Aeris's 1st limit
Reach level 99 with any character
Get Cloud's last Limit Break
Get Barret's last Limit Break
Get Tifa's last Limit Break
Get Red XIII's last Limit Break
Get Yuffie's last Limit Break
Get Cait Sith's last Limit Break
Get Cid's last Limit Break
Get a Gold Chocobo
99,999,999 Gil
Get Aeris's last Limit Break
Win your first battle