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