Quirkless Villain/Vigilante Izuku
Izuku is still quirkless. Neglectful and emotionally manipulative/abusive Inko, Hisashi left for milk and didn't come back. Izuku does meet All Might, and the interaction goes similarly, but after All Might leaves Izuku he's just disappointed that his idol turned out to be quirkist and heads home. Bakugou winds up in the hospital for a few days but survives and thanks to healing quirks is mostly back to normal.
Now, Izuku doesn't make it home like he thought he would. He's contemplating suicide when he comes across another quirkless person (red shoe theory), who had jumped off of a building and was dying. Instead of immediately calling for an ambulance like most people would, Izuku talks to this person. They decide that they still want to die, and plead with him to not call emergency services. Izuku agrees, and stays with the person until they die to comfort them and give them peace in their final moments.
Izuku decides to take this as his new purpose in life- helping other quirkless people like him and that person. He goes onto the black market and gets quirk enhanced pills that completely numb a person within minutes. He sneaks out at night, going around with a knife, and approaches quirkless people who are dying or are about to commit suicide, and offers them a choice:
He can get them help, he can kill them, or he can just stay with them until they die.
They can choose any option at any time until they die, including changing their mind. Since the pill takes a few minutes (give or take ten) to activate, he talks to them during that time. He lets them vent and just say what's on their mind.
Now, heroes and police and basically everyone (bar the quirkless people he helped that remained alive) believe that he's committing hate crimes, thinking that he's a quirkist extremist. They don't realize that the deaths are mercy kills, and almost assisted suicide.
He's also a vigilante that saves everyone, but most of his focus is on quirkless people.
Aizawa and Tsukauchi are among the people assigned to Izuku's case. Poly relationship Mic/Aizawa/Tsukauchi, with married EraserMic and boyfriends Aizawa/Tsukauchi (Aizawa is the hinge of a V). Shinsou has two lovely adoptive moms. Good big brother Dabi gets custody of Shouto, and Rei is eventually allowed to leave the hospital.
Past Mic/Aizawa/Shirakumo, and good league of villains. Izuku becomes friends with Himiko and Dabi during vigilante work and friends with Shigaraki over gaming, then gets introduced to the rest of the league. Kurogiri is not Shirakumo, nor a nomu. He was a normal quirkless man who was in a bad accident and trauma manifested a quirk, and was later recruited to work for All For One. Also, AFO is dead- All Might successfully killed him.
Support course Izuku with Izuku and Mei friendship + Agender Mei! Nonbinary Tsu (Xe/Xem) and Demiboy Shouto! Plus aroace queerplatonic TodoShinDeku. TsUraka, IidaSero, KiriKami, MomoJirou, MinaMei, Hagakure/Ojiro. And probably more.
All Might bashing! Bakugou bashing but eventual redemption. Aldera bashing. Nedzu comes off as a bit of a dick at first, but warms up to Izuku. Sir Nighteye is a dick.