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