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.
Author Appeal: Apparently, Naosuke really, really liked the naginata, as he said that he wanted to turn Maki Baian, the first enemy encountered, into a recurring character. So, it's not surprise that the strongest of Jinsuke's bodyguard is a naginata master who trained Baian and comes close to killing the main character (and survives).
Complete Monster: Ryuugo Daimaru, also the Daimyo Naosada Washizu. The second part of the Unabara tournament involves a fierce battle amongst the ten surviving Ryuu. In order to win they must kill one of his sons and bring his head as proof. Understandably, his sons weren't amused.
Sasuke Sakakibara. A kid who slaughtered all his colleagues to test his spear and get the place. He comments on how easily it was to tear out a man's heart from his chest.
Jinsuke Kurogane. According to Nachi, of all the martial artists he's seen so far, he's both the strongest and the most wicked. Many people liken him to a devil. He also killed the majority of the Ogame school merely because they didn't side with his somewhat noble cause of waiting to have martial arts not die out in the age of peace, as well as having no hesitance about wanting to kill his son/
Mario Kujou: At least, Jinsuke sincerely believed in what he was doing when he killed his allies in order to maintain swordsmanship, but Mario wanted political power, so he backstabbed not only his Ogame allies, but his fellow Muhyo aides in his ambitions. Plus, he has no honor, something even the most depraved people like Muraku or Jinsuke had, having his guards ambush Kai during their fight. In a series filled with fighters who dedicate themselves to the sacred grounds of battle, Mario stands out as a manipulative mastermind using his allies for stepping stones and using dirty tricks to win fights.
Fridge Brilliance: At first, the fact that there are 31 schools in the first turn and Gama's group consist of 4 schools seems a terrible mathematic failure... then you can realize that it's perfectly possible if all the other groups are composed of 3 schools each and the one containing Naoyoshi, who's The Unfavourite, so they wanted to increases the chances of his defeat. Furthermore, Jinsuke was behind the whole thing, meaning that he wanted to test Gama's skills.
Ho Yay: Considering that there're only two or three major female characters, this is inevitable.
Gary Stu: Iori is even worse, he dominates each individual fight he's in.
Moral Event Horizon: Mario crosses it, not only admitting he killed his Muhyo allies for political gain, but later has his men ambush Kai, showing he doesn't even have the same honor of a warrior that even a depraved Blood Knight like Muraku had.
Nightmare Fuel: Sasuke, when he gets seriously into a fight. The fact that his spear can behead, maim and rip hearts out only add fuel to the fire.
After taking the first two Juugan pills, Ryuuhou turns into an unstoppable brute with red eyes and enormous force, who jumps into the fray by ''crushing" one of his surviving underlings. Then, he takes the injection, gaining Dissonant Serenity as his eyes bleed out.
MurakuMatsumoto during the whole second fight against Gama. Picture this: you're fighting an insane, sadistic bastard armed with long chains tipped with iron weights capable of turning your brains into pudding anytime. He's wearing a mail made from the hair of all the guys he "loved" and killed before they grew too old and if you lose you're going to be "added" to it. Even after getting seemingly killed by a sword in the gut, he still stands up again in his worse Limp and Livid performance babbling about how Gama must "become one with him now". Eeeeek!