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