A/N: This story contains manga spoilers at the time of publishing. Viewers be advised.
"Izuku, I'm sorry. It's my fault you don't have a quirk-" Inko said.
Out of nowhere, Izuku slapped his mother.
Inko gasped.
She saw stars, the universe, math equations. She was enlightened.
"Mom! I'm sorry, I don't know what came over me." Izuku said.
"Son, I understand everything perfectly now. How corrupted the quirk society is with discriminating against quirkless people. I should never apologize since there is nothing wrong with you." Inko said.
Izuku smiled.
"But Izuku. Don't ever do that ever again!" Inko said.
Izuku nodded.
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"Hah! Worthless Deku! You don't even have a quirk!" Katsuki said.
Izuku instinctively slapped him.
"Oh no! Kacchan, please don't hit me-" Izuku said.
"Me?" Izuku questioned.
Katsuki started to cry. Izuku had never seen Kacchan cry before.
"I'm sorry Izuku, I shouldn't have bullied you for being quirkless. That's out of your control. I think I have anger issues or something. I need help." Katsuki sobbed.
Katsuki ran off crying. He was so embarrassed.
"Huh?" Izuku said as he looked down at his hand.
A mischievous smile formed on his face.
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A few years have passed and Izuku was in his last year of middle school.
"Can I be a hero without a quirk?"
All Might, of course, told him 'No.'
Izuku frowned.
"Can you-" Izuku said while gesturing to All Might to bend down to his level.
Furious, Izuku slapped All Might for his terrible response.
"I'm so sorry! I thought I was being realistic. I now realized Nana would kill me if she heard what I said. Tell you what kid, UA is letting quirkless examinees take the Entrance Exam. Prove to the world you can be a hero without a quirk!" All Might said.
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Izuku got into the U.A no problem.
He has now decided to use his slap to fix the hero school.
His next victim was Aizawa.
"Midoriya?" Aizawa said as the young greenette approached him.
Izuku quickly and without fail slapped his homeroom teacher, shocking him.
"What the f-" Aizawa shouted.
Aizawa gasped when everything in his head clicked.
"I'm such a bad teacher! I should teach you guys how to fight. I also need to get my life together by getting enough sleep and by not overworking myself. I should see a therapist!" Aizawa cried.
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During the USJ
"All Might must die!" Shigaraki shouted.
Izuku teleported out of nowhere and slapped the shit out of Shigaraki.
"Oh fuck!" Shigaraki said.
Izuku was patiently waiting for the slap's effect to kick in.
"All Might isn't the problem. My grandmother abandoned my father so she can protect him from All For One." Shigaraki said.
The blue-haired man started to cry.
"Kurogiri, let's go home." Shigaraki sobbed.
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Everything was fine until Izuku started slapping his fellow schoolmates.
"1A sucks!" Monoma said.
Izuku, of course, gave him a good smack.
"Oh my God! I can't believe I stereotyped a class just because of Bakugou's behavior. I apologize." Monoma said.
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Izuku was in the hallway when he heard someone mutter something to themselves.
"People think I have a villainous quirk. There's no way I can be a hero!" Hitsohi ranted.
Izuku quickly corrected him with a slap.
"Oh shit!" Hitoshi said.
He's pretty sure he saw Heaven flash before his eyes.
"I'm so stupid! Any quirk can be used for evil. There's no such thing as a villainous quirk." Hitoshi insisted.
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"I can't use my right side during battle. I hate my father!" Shoto ranted.
Izuku sighed.
" A troubled youth. " Izuku thought.
The same old, same old happened after Shoto was slapped.
"I'm so stupid. It's my quirk, not his!" Shoto said.
"Dumbass." Izuku chuckled.
"Thanks, Midoriya." Shoto said.
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Izuku even got his friend Tenya.
"I must kill Stain! He put my brother out of commission." Tenya said.
"Bitch!" Izuku said as slapped Tenya.
"Midoryia! Why-" Tenya said.
Tenya gasped.
"I can't believe I almost threw my life away trying to seek revenge. My brother would be so ashamed of me." Tenya said.
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While on patrol, Izuku came face to face with the Stain.
"Hero society is corrupted. I must take out the trash!" Stain said.
After being slapped, Stain realized how foolish his plans were.
"I should have been advocating changes. My message won't get across if people think I'm just a bloodthirsty murderer. It would only push people to become villains." Stain said.
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Somehow, the League of Villains still formed.
"Run!" Himiko shouted.
Izuku was terrorizing the villains by chasing after them and threatening to slap the sense into them.
Thankfully, Kurogiri warped the villains out before their redemption arc started.
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At Kamino Ward
"I used to rule the underworld of Japan. I'm not even sure what I want anymore but I still want to kill All Might." All For One said.
All For One was taken back when he saw the young greenette appear right in front of this.
After having the hell slapped out of him, All For One started to cry. Hard.
"I miss my brother. I also need therapy!" All For One said in-between sobs.
The World was shocked.
A quirkless kid defeated a powerful supervillain with a mere slap.
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Eventually, Sir Nighteye allowed Izuku to intern at his agency as long as he promised he wouldn't slap him.
While on patrol with Mirio, they came across Overhaul and Eri.
"You!" Overhaul said.
Overhaul's legs were shaking in fear. This was the same kid who took down All For One.
Izuku raised his hand.
"No! Please! I beg you."
Izuku sighed and put his hand down.
"What do you want? Money, Drugs, Girls?" Overhaul said.
Izuku shook his head.
"No, please!" Overhaul cried as Izuku raised his hand again.
As expected, Izuku slapped the shit out of Overhaul.
They had to call the paramedics because Chisaki was crying and was delirious.
"Can your slap do psyche damage?" Mirio asked.
Izuku looked down at his hand.
"I don't know." Izuku said.
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A few weeks later, Shoto invited Izuku and Katsuki to intern at his father's agency.
" I feel…bold today. " Izuku thought.
Now, on patrol with his friends and Endeavor, Izuku met Hawks for the first time.
"Ooh. Cool. You're that slapping kid." Hawks said.
Izuku had a sudden strong urge to slap Hawks, which he did.
"Oops." Izuku said as he saw Hawks have a mental breakdown.
Keigo was muttering things about being groomed and how corrupted the Hero Commission is.
Izuku was furious.
He later goes on a rampage at the Hero Commission's Headquarters and slapped everyone he lays his eyes on.
"You're next President!" Izuku said as he rose his hand.
"Midoriya! You don't know what you're messing with." Public Safety Commission President said.
"Try me!" Izuku said.
After getting double-slapped, the Public Safety Commission President blew the whistle. All of the Hero Commission's misdoings were revealed.
Izuku ends up winning a Nobel Peace Prize for being the spark that led to the reformation of the Hero and Quirk Society in Japan.
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"Izuku, I'm finally home!" Hisashi said.
Izuku was beyond furious.
How dare his father walk back into his life only after he became famous.
Izuku ran up to his so-called father and gave him the slap of his lifetime.
The slap heard around the world.