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