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.
Adaptation Displacement: Western audiences are much more familiar with Doomed Megalopolis than the other adaptations, and you'd be hard pressed to find anybody who knows about the books. Justified, as the books and a few of the films have never been translated into English.
Cut-and-Paste Translation: The English version removed a lot of the cultural context from Doomed Megalopolis, as they thought it might confuse western audiences. Unfortunately, it just made things even more confusing.
Everyone Is Satan in Hell: Thanks to the use of pentagrams, some people have accused Doomed Megalopolis of "promoting Satanism." This is despite the fact that eastern religions are the faiths featured in the series, not Abrahamic ones (from which western Satanism is derived). Not helping anything is the box art◊, which prominently features Kato's Nightmare Face and a pentagram on his glove.
Evil Is Cool: Kato is all over this, right down to his stylish clothing (one of his outfits in The Last Megalopolis had dragons on his shoulders!), scary magic powers, and legions of monsters at his command. He's also surprisingly tough to boot. More than likely, this is the reason why he's a Fountain of Expies.
In Doomed Megalopolis, one of Kato's shikigami looks like two Assy Mcgees stitched together.
Some of the goofy-looking faces Kato makes in the live action movies while casting magic, particularly in The Last War. This was even parodied by Japanese comedy duo, the Tunnels. In one of their skits, a band of Kato impersonators wearing Paper Thin Disguises start tearing up Tokyo while making the silliest faces possible.
The OVA is full of this. First, there's Kato's trippy Mind Rape attacks. Then there's the stomach worm that Yukari coughs up. Then there's the rape scenes that are very much there to disturb the audience, and not for titillation.
The Last War features Yukiko's nightmare within a nightmare in which a Kato clone turns her adopted little sister into a bug and steals her body. She follows it, only to find another clone bursting out of the injured Nakamura's chest. She wakes up only to find the real Kato standing right behind her with her sister who is still a bug, and he promptly rips her tail off.
Despite the original novel and The Last Megalopolis being pretty light on horror, the OVA adaptation Doomed Megalopolis is renowned for pushing its gross-out content to the limit. The fukuchu-mushi has a phallus-shaped head and is vomited up by the female lead, a hideous bug monster bursts out of a nurse's body, rape serves as a major plot point, etc.
The Last War also has some rather gross, gory moments such as when Kato tortures Nakamura by psychically breaking his bones, Yukiko rips off part of Kato's face, making his eyeball dangle, and Nakamura defeats Kato by forcing a Chest Burster down his throat, causing his head to implode.
Whole Plot Reference: To Dracula. Both stories involve a supernatural immortal villain who feasts on the living to maintain his immortality, an innocent girl who is target of his plans, a group of people who try to protect her out of love, and a wise man who knows the antagonist's nature and the way to defeat him. Those references are not surprising, as Hiroshi Aramata was mentored while in the college by the scholar who translated Dracula to Japanese.
Yukari. She suffers from visions of disasters in the near future, is repeatedly kidnapped and Brainwashed by Kato to serve as Lord Masakado's medium, and is impregnated by her brother, no less! Things are made even worse for her in Doomed Megalopolis, when she raped repeatedly and is Driven to Madness, becoming all but catatonic in the final episodes.
Yukiko. At a young age, she is stalked by Kato and eventually kidnapped by him. In Doomed Megalopolis, she is almost sacrificed to the underground dragon, and almost killed by her father, Yoichiro. In Tokyo: The Last War, we see the extent of her trauma: she's scared of men in military uniforms (especially if they're wearing capes), and still has nightmares about being kidnapped. To top it all off, her best friend is gunned down right in front of her face during an Allied air raid, and her boyfriend dies trying to get rid of Kato.