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