Here is the full list of all 22 99 Levels To Hell achievements.
Used a cheat code
10 hours in the dungeons
Die 100 times
Collect 10.000 gold
Found all the hidden books
Beat the Devil
Found the Dragon
5 hours in the dungeons
Beat the 9th boss
Beat the 6th boss
Beat the 7th boss
Beat the 8th boss
Beat the 5th boss
Found the Hunter
2 hours in the dungeons
Beat the 4th boss
Spill 1000 liters of blood
Beat the 3th boss
Beat the 1st boss
Beat the 2nd boss
Found the Major
Ghost?