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