Here is the full list of all 42 Romancing SaGa 2 achievements.
Befriended a Strategist
Befriended a Saigo Clansman
Befriended a Crusader
Befriended an Armed Merchant
Befriended a Brawler
Defeated Kzinssie
Gerard became Emperor
Defeated the Watchmen
Befriended a Vagabond
Befriended a Mage for Hire
Befriended an Imperial Guard
Befriended Coppelia
Coppelia became Emperor
Befriended a Nereid
Befriended a Diver
Befriended a Nomad
Befriended a Desert Guard
Befriended a Hunter
Befriended a Mole
Befriended a Salamander
Befriended an Amazon
Befriended an Iris
Befriended a Levante Guard
Befriended a Ninja
Befriended a Diviner
Became the Final Emperor
Defeated Bokhohn
Defeated Noel
Defeated Dantarg
Defeated Subier
Defeated Rocbouquet
Defeated Wagnas
Acquired Dark Magic
Finished the Game
Nurtured the Avalon Tree to the fullest
Defeated Crushing Memory
Defeated Evil Memory
Defeated Ruined Memory
Defeated Sinful Memory
Finished Game without Final Emperor
Won Against Victor
Defeated Dread Queen