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.
YMMV: Majin Tantei Nougami Neuro
Awesome Music: Kodoku no Hikairi the ending song of the anime, which translates to "Light Of Loneliness" which fits the feeling of Yako's purpose in life being filled by Neuro very well, as well as describing Sasazuki, HAL and Sai's loneliness
Dirty, the opening of the anime, captures the action and insanity of the series.
Complete Monster: Sicks absolutely revels in his evil. A monster from birth who slit the other babies' throats in his nursery and later murdered both his parent Sicks comes into conflict with the Anti-Hero demon detective Neuro. Sicks tracks down his clone, X, and murders X's love, infiltrating the police by wearing the skin of a man he killed. he punishes a subordinate who had failed to find X by making him saw himself open with a rusty saw, admitting he didn't care about a fair punishment: he just wanted to see the man die. To present a meal for Neuro, a demon who eats mysteries, Sicks forces a mansion's worth of people to commit murders in that lacked creativity, being straight forward slaughter...and then blew them up when Neuro was repulsed by the gesture. When recruiting his 'Fingers,' Sicks presented one with a cube made of the faces he had ripped from everyone close to him, and with another he forced him to murder his own father. He later kills Sasazuka by shooting him in the face, but not before subjecting him to severe Shape Shifter Guilt Trip by having Sai turn into his family For the Evulz and is revealed to be the one who was responsible for Setsuna, Harukawa/HAL's lover's death by brain degeneration through a experimental drug he concocted. Sicks' goal was nothing less than the absolute annihilation of humanity as well and on his orders, Japan suffered catastrophic death tolls before he and Neuro finally engaged in a Duel to the Death.
Cult Classic: A moderately popular in Japan, the only things it released state side is a Viz license on the anime and not a dubbed version. That being said, it does have an interesting concept on the Monster of the Week storyline being necessary and the depths that Card-Carrying Villain-y can sink to.
HAL and especially Sicks, a rare example that counts as a Complete Monster as well
Mind Game Ship: As pointlessly cruel as Neuro is to Yako, it almost comes across as affectionate as the series goes on.
Judging by the demonic date sim Neuro once played, pointless cruelty is his way of showing affection. And of course, Yako appears in Neuro's wet dream right next to the ultimate puzzle once.
Moe: Miyasako Mutsuki, a little girl who wants Yako to help her grandfather.
Moral Event Horizon: Sicks was never a nice person but what REALLY seals the deal is how he murdersSasazuka by having Sai briefly inflict Shape Shifter Guilt Trip by shifting into the forms of his family before finally shooting him himself...
It's then revealed that Setsuna's degenerating brain was caused by one of Sicks' drugs, thus is responsible for Harukawa's Freudian Excuse
Hell, he may very well have set a record in how fast he crosses it. Namely, slitting the throats of a nursery full of newborns with a razor blade hours after he was born.
DR crossed it when he willingly causes a flash flood, killing off a large percentage of the population of the city where Yako lives. Even Neuro with his Thou Shall Not Kill policy, thought that he should die for doing that.