Here is the full list of all 42 Romancing SaGa 2 achievements.
Finished the Game
Defeated Noel
Defeated Subier
Befriended a Diver
Became the Final Emperor
Defeated Rocbouquet
Defeated Wagnas
Befriended a Nomad
Defeated Bokhohn
Befriended an Imperial Guard
Befriended Coppelia
Defeated Dantarg
Befriended a Salamander
Befriended an Iris
Befriended a Mole
Befriended a Levante Guard
Befriended a Desert Guard
Befriended a Nereid
Befriended a Crusader
Befriended a Hunter
Befriended a Mage for Hire
Befriended a Strategist
Befriended a Saigo Clansman
Befriended an Armed Merchant
Befriended an Amazon
Befriended a Vagabond
Befriended a Brawler
Defeated Kzinssie
Gerard became Emperor
Defeated the Watchmen
Coppelia became Emperor
Befriended a Ninja
Befriended a Diviner
Acquired Dark Magic
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