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