Here is the full list of all 21 Etrian Odyssey II HD achievements.
Reached the First Stratum.
Obtained all other achievements.
Reached the Second Stratum.
Reached the Third Stratum.
Reached the Fourth Stratum.
Reached the Fifth Stratum.
Reached the Sixth Stratum.
Defeated the boss of the Sixth Stratum on Expert difficulty.
Encountered an enemy through mining ore, gathering plants, or chopping wood.
Defeated the Overlord.
Defeated the Ur-Child.
Retired an adventurer.
Let an adventurer rest.
Obtained more than 250,000 Ental.
Completed the quest "The beautiful Queen".
Dealt 1,000 damage with a single hit.
Defeated a boss in a single turn.
Defeated the Wyrm.
Defeated the Drake.
Defeated the Dragon.
Unlocked the Beast class.