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