Katsuki Bakugo

Katsuki is a crude, arrogant, short-tempered, and aggressive person, especially at the beginning of the series. Katsuki tends to come off as unheroic; this problematic behavior going all the way back to his early childhood days when he was known to bully a young, Quirkless, Izuku Midoriya. He showed to be extremely arrogant and condescending to those around him, often bragging of his Explosion Quirk's power, and even boasting that he would take on his entire middle school class. He showed open hostility towards Izuku, mainly because of his former Quirkless status, and would frequently put down his dream of becoming a Hero, despite lacking a Quirk, and also gave him the insulting nickname "Deku" (meaning useless and unable to achieve anything). He even threatened Izuku not to apply to U.A. High School and became angry upon both of them passing the Entrance Exam, wanting to be the only person from his middle school to make it there.

However, after being accepted into U.A. and experiencing several personal defeats, one of them even coming from Izuku, Katsuki has gradually changed into a less antagonistic person, albeit still retaining a lot of his unpleasant traits. While often portrayed negatively, Katsuki's fierce character and competitive drive have actually granted him an important role among Class 1-A, as a sort of inspirational mood-maker.