Here is the full list of all 36 Grandia II Anniversary Edition achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Find Elmo in the Birthplace of the Gods
Defeat the Egg Guardian
Have 250,000 gold at one time
Defeat the Heart of Valmar
Defeat the Body of Valmar
Drink 100 Potions
Find the Exorcism Bow in Demon's Law
Kill 1000 Monsters across all playthroughs
Defeat Melfice
Add Tio to the party
Defeat Valmar's Claw
Win an arm wrestling bout
Defeat Valmar's Eye
Have a party made up of Level 25 or greater characters
Defeat Valmar's Tongue
Have a party made up of Level 10 or greater characters
Add Mareg to the party
Find Roan's missing medal
Add Roan to the party
Add Millenia to the party
Escort Elena to Garmia Tower
Level Up
Add Elena to the party
Congratulations! You pressed the X button. It doesn't do anything... or does it? No, it doesn't.
Kill 2000 Monsters across all playthroughs
Have a party made up of Level 50 or greater characters
Grab 24 nuts on the final test in the Hut of Trials
Defeat Melfice with only Ryudo delivering damage
Defeat Valmar's Core
Defeat Zera Valmar
Complete Grandia II with difficulty on Hard the whole time
Find the Coral, Demon, Forbear, Friends, Pretty, and Rune Necklaces
Find the Black, Heracles and Sonic belts
Change a character's outfit during combat (Weapon, Accessory & Mana Egg)
Max all abilities in a Skill Book
Max all abilities in a Mana Egg