These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel — The entire series, pretty much cover to cover. You know those small "Explicit Content - Parental Advisory" stickers that cover most mature manga? For MPD Psycho, it fills half the front cover!
Although, the certain volumes that do have this sticker also have mutilated, naked women on them.