Here is the full list of all 45 Final Fantasy VIII achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Finish the game
Beat the Omega weapon
Collect all cards
Learn all of Rinoa's limit breaks
Kill 1000 enemies
Reach maximum Gil
Unlock Guardian Force Doomtrain
Unlock Guardian Force Cactuar
Collect all Weapons Monthly/Combat King/Pet Pals/Occult Fan magazines
Collect all Timber Maniacs magazines
Unlock Guardian Force Alexander
Draw magic 100 times from draw points
Unlock Guardian Force Eden
Reach maximum HP
Unlock Guardian Force Bahamut
Complete the Obel Lake side quest
Reach level 100
Learn all of Quistis' limit breaks
Reach level 100 with Boko
Complete the PuPu side quest
Find Ragnarok
Unlock Guardian Force Cerberus
Unlock Guardian Force Tonberry
Unlock Guardian Force Pandemona
Acquired an item from Chocobo World
Capture a Chocobo
Defeat every member of the CC Group
Win 100 games of Triple Triad
Unlock Guardian Force Leviathan
Reach SeeD rank A
Unlock Guardian Force Carbuncle
Unlock Guardian Force Brothers
Upgrade your weapon
Kill 100 enemies
Unlock Guardian Force Diablos
Get your first salary from SeeD
Unlock Guardian Force Siren
Lose a rare card in a Triple Triad game
Unlock Guardian Force Ifrit
Draw (Stock) magic from enemies 100 times
Play Triple Triad
Unlock Guardian Force Shiva
Unlock Guardian Force Quezacotl
Finish the game with Squall's initial level
Kill 10000 enemies