Here is the full list of all 20 Dead Dungeon achievements.
Die 1000 times
Die 500 times
Collect all collectables
Find the first secret level
View credits
Defeat the boss
Collect all donuts
Kill 100 enemies
Complete 40 levels
Find the second secret level
Complete 30 levels
Activate the trap
Complete 20 levels
Die 100 times
Use the portal
Complete 10 levels
Kill the enemy in an unexpected way
Kill the first enemy
Find first collectable
Die for the first time