Here is the full list of all 15 bit Dungeon II achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Kill a mini-boss.
Enter into the Dark World.
You have died. You have all lost things. You can not take your possessions with you to the next incarnation.
Find an epic-quality weapon.
Reach level ten.
Free the ghost from her grave.
Slayed the Fiend.
Kill the leader of the Thief Kings, The Cursed Wizard!
Destroy the Soul Collector.
Kill the king of Skeletons.
Slay the Fire Nob Glob.
She rules an army of beasts in the Black Church, defeat The Yaldabaoth.
Face The Eater!
Slay the Demiurge.
Tis this a demon?