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: Tonari no Kaibutsu-kun
Designated Hero: To some Haru, whose first response to an obstacle is usually threats or violence, threatens Yamaken with breaking his arms and legs if Shizuku chooses him, threatens to rape Shizuku of all things in one of their earliest interactions to get her to keep quiet, and acts violently numerous times, sometimes with a side effect of accidentally hitting Shizuku out of all possible targets. And he's still being viewed as cute by fans and is criticized In-Universe more for being "too spontaneous" or "irresponsible" rather than a sociopath.
Draco in Leather Pants: Yamaken is easily one of the more popular characters in Japan, placing first in the most recent popularity poll, though he is introduced as a bully early on in the story and at first grows to like Shizuku out of spite for Haru. He gets more Character Development as the story continues, but he still remains a jerk throughout the bulk of it.
Ensemble Darkhorse: Natsume, for being so sweet and awkwardly funny while also greatly desiring her friends' love and attention, and meddling a bit too much in their affairs to get it, though she is well-meaning. She is surprisingly relatable to and popular among many fans.
Hollywood Homely: Shizuku is stated to be plain and have the fashion sense of a grandma, but she's still rather attractive to Haru and Yamaken.
Ship-to-Ship Combat: Fans are split between Haru and Yamaken when it comes to who they wish Shizuku would end up with, usually preferring Shizuku with the character that they like more.