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