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.
Complete Monster: The eldest of the Gowa children, Kazukiyo, who goes so far as to assassinate a Minister of Justice in what looks like a tragic road accident, have soldiers injected with Psycho Serum and forced to pilot the series' mecha for 36 hours straight, provide assistance to Well-Intentioned Extremist allowing him to stage a coup, use his own sister in an experiment (something that another of his brothers refused to do, and commit patricide in a very cruel way (and in front of said little sister) in order to achieve his goal.
His very ancient predecessor, Tsuna Watanabe, isn't any better, deliberately having the city of Kyoto set on fire, letting the firestorm of Gasaraki be summoned and then torturing Yushiro by shooting him in the knees with arrows when he refuses to let the summoning continue.
Nightmare Fuel: During the final battle, where the artificial muscles in Yushiro's TA break out of their confines and begin wrapping around the opposing Mecha to merge with it's artificial muscles, the end result is the enemy mecha getting crushed in a bearhug.