Here is the full list of all 11 HENTAI HELL achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
You've killed 100 hentai enemies.
You've killed 75 hentai enemies.
You've killed 50 hentai enemies.
You've survived for 100 seconds.
You've killed 25 hentai enemies.
You've survived for 60 seconds.
You've survived for 40 seconds.
You've killed 10 hentai enemies.
You've survived for 25 seconds.
You've killed 5 hentai enemies.
You've survived for 10 seconds.