When I first started writing, I wanted someone interesting and complex, and I thought of Shigaraki. His powers are strong, yes, but only if you are close to him and he can actually grab you. Otherwise, it's not strong since guns can just kill him (unless we mention his awakening, I address that below)
Then I remembered his awakening and thought he would once again be another overpowered person, but then I decided no, I would just keep his only five-finger touch decay. This way, there is still the tension of him having to fight close and not just one shotting everything, otherwise what's the point of the book.
SOOOOOOO, his awakening abilities will be uncontrollable. They will basically release high, intense emotions, but because they are uncontrollable, anything around him, including allies, will decay.
Maybe by the end of the book, he can control it, but for the majority, he won't be able to.
If you want to learn more about Decay, look at the My Hero Academia Wiki - Decay.
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Finally, we have the League of Villains; as of Chapter 6, he has mentioned he wants to create one, just like the show. So, who should be a part of it? That's the question... let's make it close to arcane related if possible; otherwise, if we add more and more characters from League of Legends, it will just be an Avengers-level threat of all good characters vs bad characters in an epic showdown battle... sounds cool, but cmon its arcane. (I'm not saying it's not doable; imagine Captain America's Civil War, but it's good heroes vs the villains, lol, but deaths would be a thing...)