The Adventures of Bomberanian, a Pokémon Named Lord Explosion Murder, and a Random Fish They Found Along the Way that Craves Violence and Bloodshed. If You Ever Wanted to Read About Kacchan Slapping a Bitch with a Live Magikarp, This is the Fic For You. (смешанная)

One day, De- Izuku just left to go on his shitty pokémon journey, leaving Katsuki behind. The explosive blonde doesn't know how to cope without the greenette somewhat involved in his life. He partially blames himself and discovers that he might have been a terrible fucking friend. Katsuki resolves to be a better person with a Heroic heart.
Sort of.
First, he needs to track down each and every bitch ass extra that dare hurt his nerd and make them regret it. Auntie approves. Petty revenge can be rather therapeutic, and can somehow lead to a bunch of convoluted shenanigans and legal loopholes pertaining to vigilantism.
In other words, Auntie Inko is a badass, and Katsuki learns to be a better person through the Midoriya tradition of borderline yandere bullshit.
(Yes, this is part of a series. Technically, The Ranger's Curse is Part 1 to the "main plot" of this AU. Bomberanian is a side story that is Bakugou's pov during Izuku's own shenanigan filled journey. While this can be read as a stand alone, I recommend you check Ranger's Curse to get a better understanding of the AU, since Katsuki doesn't embellish on world building in his pov.)