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