Here is the full list of all 30 Mystery Chronicle: One Way Heroics achievements.
Clear any world other than the tutorial on Easy.
Defeat 200 monsters on 1 adventure.
Take 3 Allies with you on your adventure.
Clear a world on Normal.
Defeat Fallen Angel Alma on Normal or higher difficulty.
Defeat 100 monsters on 1 adventure.
Expand the castle.
Gain ability to customize the castle.
Acquire all trophies.
Clear a world on Hard.
Clear a world on Very Hard.
Defeat Zeukrees, the Giant of Light.
Defeat Pluton.
Reach the End of the East.
Reach the End of Dreams.
Reach the end of the world.
Recruit all residents.
Complete a quest that unlocks a class.
Unlock all classes.
Clear on Normal or higher difficulty with all classes.
Open 50 treasure chests on 1 adventure.
Open 100 treasure chests on 1 adventure.
Expand Dream Vault to maximum size.
Defeat the Bug Emperor.
Battle another hero in an online match for the first time.
Battle in 10 online matches.
Win an online match.
Win 10 online matches in a row.
Obtain an extra medal.
Unlock all epilogues.