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