This achievement is best paired with the higher difficulty achievements "Super Hero" and "Uber Hero" for beating the game on 'I am death incarnate!' and 'Uber' respectively. In my personal opinion the hardest part of the game is the latter section after the whole 'ritual' ordeal. (And the final boss fight!)
Here's the thing though, you don't actually need to play the full game on a select difficulty for that. You simply need to go ahead and beat the game and reload the last level and beat that on 'Uber' or 'I am death...' and beat the level to kill 3 birds with one stone per say.
YouTuber "randomChievos" has a pretty good route you can take on that level for 'Uber' that should help.