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