Here is the full list of all 21 NeverEnd achievements.
Kill every mini boss in one run
Get 20c in one run without the Rod
Finish the second quest
Buy a Bow and a Rod in one run
Walk through 100 rooms in one run
Finish the first quest
Walk into a room with 6 Zomborgs
Find one elemental sword
Kill your first mini boss
Buy your first item
Kill your first enemy
Die in the first 10 seconds
First death
Buy all items
Collect all hats
Konami code
Beat the game
Complete the game with the stick
Kill the dummy
Kill 50 enemies with the bow
Kill the final Boss