I've got some finished BNHA fics to recommend.
Hero Class Civil Warfare by RogueDruid
Heroes lead by Bakugo.
Villains lead by Midoriya.
Seven days prep time.
Three days for Izuku Midoriya to show why they should be glad he's not a real villain.
Taking place before the final exam, class 1A and 1B are combined for a multi-day heroic/villain scenario. This is an excellently entertaining story with Mastermind Midoriya, rule-lawyering, munchkining of Quirks and combinations, and a great progression of action and intrigue. Has two sequels, one of which is also complete.
Intersection has the students/teachers from the Civil War story transported to canon BNHA, so its student body versus student body and a showcase of just how many changes have resulted from the Civil War.
Hold Your Breath by ElpisLumina
A crossover with Kimetsu no Yaiba. The Demon Slayers won. Muzan was killed. But Nezuko remained a demon. Outliving her friends and family, Nezuko remains detached from the world, until she offers to babysit her neighbour Midoriya Izuku. A "Izuku trained as a Demon Slayer" fic, it also features descendants of the Demon Slayer Corps in modern times and a Tomura who wasn't taken by All For One, so the League of Villains has a different leader.
journey to the past by aloneintherain
Izuku is five years old the first time he's saved by heroes. He's an instant fan of the woman in pink with her cheerful smile and the man with his ice powers and fine-boned features, even if they both refuse to tell him their names.
For most of his life, Izuku has been the centre of villain attacks, but he has never been injured. Every time, he's saved by bright, unknown heroes—heroes who smile at Izuku, and ruffle his hair or ply him with hugs, and seem mesmerised by how small he is.
Heroes that the rest of the world doesn't believe exists.
(Time-travelling Class 1-A AU)
Really good experience reading this. Seeing little Midoriya meeting all his grown-up classmates (and then meeting them
again as teenagers) was very cute and well done. Time travel doesn't change too much from canon, just little things here and there. Has a few plot twists that don't alter too much and only improve upon the story when they are revealed.