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 Elementary School Principal, Kuonji. Kidnapping, extortion, blackmail, child abuse, child slavery, etc. He's not a good person. At first, he turned Luna against Yuka and made them enemies. Then, after Yuka's stealng alice was discovered, he forced her to go on missions and steal the alices of dying/dead people. He was also responsible for Izumi Yukihira's death, practically brainwashed Rei, AKA Persona, implied to be responsible for Kaoru's death, burned Natsume's hometown by making Aoi's alice go out of control and held her hostage to ensure Natsume's loyalty, caused Yuka's death, and severely injured Narumi. He's currently holding Mikan hostage, preventing her from using her alice to heal Nobara. Oh, and his clone is the boss of the Z organization, which kidnapped Natsume and nearly killed Hotaru.
Goshima arguably crosses it when he murders Yuka on the ESP's orders.
The Woobie: Mikan, especially when she first enters the school and has to bear plenty of snobbery from the other students and a crappy dorm room. Things gravitate from worse to better as the plot progresses, though she has friends to back her up and protect her heavily by then.
Most of the Dangerous Ability students could fit this, to some extent. Especially Rei