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