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.
Chief Ekoda is the head of the Tokyo Police Department, who hides a secret fetish: He has a thing for legs. In fact, while a member of Suitengu's Roppongi Club, Ekoda took the chance to satisfy his feitshes by kidnapping women, holding them hostage and then cutting their legs off before preserving them as trophies, molesting and killing the women himself. His first two victims were his own wife and daughter. Later in the series, Ekoda kidnaps Ginza Hibari and tries to do the same to her before she frees herself. Ekoda is set apart by being a completely human monster, and his insane excesses make even the hardened Ginza reevaluate everything she had done to this point.
Mizunokuchi is a sadistic dentist who, as a Euphoric, is granted a multitude of spider-like limbs that he can turn into drills. In the past, Mizunokuchi operated on heroine Kagura when she was due for dental surgery, removing her lower molars while she was still conscious so he could feel her pain. In the present, the dentist takes pleasure in outright tying patients down and simply torturing them to death by drilling through their mouths. He even takes disturbing trophies of the teeth that he carves and polishes afterwards.
Ran Yurigaoka is an esthetician with a thing for tattoos and body art. With his Euphoric powers, he can make his tattoos come to life. Yurigaoka uses them to control other people, playing them as People Puppets for his amusement. His real joy, though, is the Giant Spider tattoo on his back. Yurigaoka uses his fame to find women and uses his powers to give them pleasure, before he paralyzes them by merging the spider with their skin. After this, he has it kill them while they're alive and conscious, but paralyzed the entire time.
Kamiya becomes Japan's Prime Minister and schemes to take possession of the Roppongi Club, which caters to every fetish and predilection of the upper classes, away from the Big BadSuitengu, while also gaining control of Kagura for his own purposes. A glutton whose power is to devour anything, before he even achieved these powers, he once drove a couple to suicide over a huge debt, and then took their children to compensate. The son he sold as a child soldier would one day become Suitengu. The girl, who was only five, he sold as a Sex Slave to be abused and debauched until she was an Empty Shell years later, knowing only how to please men and request money for it.
Crazy Awesome: Seriously, some of the ways Saiga comes up with to wreak havoc with a camera are truly mindboggling.
In-universe, the screeching of dentist drills — Niharii is shown cowering in an office with his hands over his ears to block out the sound. Of course, the fact the drills were being used by a Depraved Dentist to basically rip a woman's mouth apart probably played a factor in that.
Ho Yay: Besides Bob, Tsujido is really attached to Suitengu. Played with more subtlety than in many anime, though.
Moral Event Horizon: Shinzen's treatment of Kagura puts her WAY beyond this point. Other Euphorics also cross this line.
Hibari Ginza when introduced, was a pretty dark Cowboy Cop who had a habit of "self-defensing"(killing the second lethal intent is shown even if there's no chance that she'd be harmed by using non-lethal methods) every violent criminal she came across and tried to blackmail Saiga into sleeping with her. So pretty disturbing stuff overall, but made less cringeworthy as it could've been given the deaths were played for dark laughs,(and they all were REAL nasty individuals) and Saiga wasn't especially bothered by her blackmail and got the better of her anyway. As she comes closer to finding out the truth, however, she shows an unhealthy obsession with Saiga and eventually trades Kagura to her abusive mother in return for "keeping" him. She then proceeds to hit him with her car, rape him while he's unconscious for what's implied to be days all while questioning why "she's not good enough for him",(How her plight tugs at the heartstrings...) and lock him up until he decides to be with her. Later on, the show attempted a Heel Realization, but most would say it was just a little too late for her to realize her treatment of an innocent girl and of course her nightly fucking rape sessions were wrong.
Nightmare Fuel: LOTS of it. An example? Anyone afraid of going to the dentist should probably avoid watching episode 8.