You know the saying 'the pen is mightier than the sword'?
Well, that does not apply here. There are no swords, only quirks.
Izuku doesn't have a quirk.
But he does have a black pen. And it is damn mighty.
Humanity has made a lot of mistakes. Messing with Izuku Midoriya was one of them.
Now they'll suffer the consequences.
And never again will anyone make that same mistake.
They won't even try,
They're not that stupid to try and challenge the one who defeated the symbol of peace.
Katsuki decided to become the number one hero, even deciding to outrank the symbol of peace, to become the one Izuku admires again, like when they were children. Coming to the realization of his true feelings for Izuku, he begins to bully him mercilessly to cover them up and try to deny them.
Things become a bit messy when Katsuki gets in the way of a ray from a man who's quirk is to make his target only able to tell the truth for 72 hours.
[Warning: there is some swearing in this! I typically don't like writing swears but for the sake of honoring Katsuki's character, there is some. Please do not read if this bothers you! Though, I assume if you watch or read BNHA, you're probably used to it.]