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