Here is the full list of all 66 Crystal Story II achievements.
Catch all the rare fishes.
Complete Chapter VI.
Use "Cyclone Dance" in battle.
Win 5 Class B Card battles.
Use "Death's Gate" in battle.
Win 5 Class C Card battles.
Defeat the boss of Sunken Ruins.
Defeat Calloc.
Use "Dragon's Rage" in battle.
Defeat the "Snowy Chillers" (Hard Mode) in the Battle Arena.
Defeat the "Highlands Flyers" (Hard Mode) in the Battle Arena.
Defeat the "Swamp Stalkers" (Hard Mode) in the Battle Arena.
Defeat the "Desert Crawlers" (Hard Mode) in the Battle Arena.
Defeat the "Small Town Gang" (Hard Mode) in the Battle Arena.
Complete Chapter V.
Defeat "The Big 3" in the Battle Arena.
Defeat the "Snowy Chillers" in the Battle Arena.
Use "Hurricane" in battle.
Complete all Wanted Quests
Use "Magic Bullet" in battle.
Use "Lucky Strike" in battle.
Successfully hack all of the hackable chests.
Defeat all match defense quests.
Defeat the "Earth, Wind and Fire" in the Battle Arena.
Complete the Trickster tree.
Use "Dragon's Breath" in battle.
Complete the Healer tree.
Complete the Guardian tree.
Complete the Mage tree.
Complete the Thief tree.
Complete the Slayer tree.
Win 5 Class D Card battles.
Use "Cursed Dagger" in battle.
Defeat the "Highlands Flyers" in the Battle Arena.
Complete Chapter IV.
Use "Snipe" in battle.
Use "Rend" in battle.
Use "Dragon's Roar" in battle.
Defeat the "Royalty" in the Battle Arena.
Defeat the "Swamp Stalkers" in the Battle Arena.
Complete Chapter III.
Defeat "The Dead" in the Battle Arena.
Defeat the "Desert Crawlers" in the Battle Arena.
Complete Chapter II.
Defeat "The Small 3" in the Battle Arena.
Defeat the "Small Town Gang" in the Battle Arena.
Complete Chapter I.
Win your first battle.
Defeat the boss of Lao Prison.
Defeat the boss of Giant Land.
Defeat the boss of Doom Lair.
Defeat Mechaslime.
Defeat Chimera Prime.
Defeat Foxer.
Defeat Seraph.
Use "Trigger Happy" in battle.
Complete the bestiary.
Complete all Wanted X Quests
Get a Gold time on Track 3 of Snowboard Extreme!
Win all Mercenary Defense events.
Complete the Secret Quest.
Win 5 Class A Card battles.
Win 5 Class S Card battles.
Win 5 Class GM Card battles.
Defeat the Card Master in a card battle.
Obtain the Number One Card.