The Downfall Hero

Prologue

A fairly unassuming class waits for their teacher to finish talking. "You're all third years now, so it's time to start thinking about your careers. I would hand out these forms, but" he throws the forms in the air, letting them scatter "you all want to be heroes." In response, everyone in class activates their less than impressive quirks, bar two students. A blonde and a greenette.
The blonde stands on his desk. "Hey, don't limp me and Izuku in with these extras, we're gonna be the greatest heroes you ever seen while these losers will be lucky to be working for some D-list sidekick!"
Izuku pulls Bakugou off the desk by his collar while the case boos him. "Kacchan, you can't say that."
Bakugo rolls his eyes half-heartedly. "Whatever nerd."

The two best friends are walking home, with Bakugo complaining. "I don't know why you stand up for those extras."
Izuku just smiles. "Someone has to keep your record clean. Besides, it's not like we're gonna see them after we graduate." The duo go down an alley as a shortcut home, Izuku seeing a bottle. "Oh yeah."
Katsuki judges his friend as he approaches the bottle. "I also don't know why you do that."
Izuku shrugs. "It's just satisfying." He jumps up and stomps down on the bottle with both feet, the lid flying off and a strange liquid spilling out of the bottle. Izuku pulls his shoe out of the sludge. "Eww. Gross."
Katsuki laughs. "That'll teach you." He suddebly gains a horrified expression as he sees something behind Izuku. "Look out!"
He pushes Izuku out of the way and gets enveloped in a kind of liquid. "Thanks kid, you're my hero. I needed a medium skin suit. Not a bad quirk neither." Katsuki reacts on instinct, sending out explosion after explosion as the villain drags him out of the alley in a wrestle for control. Izuku tries to follow behind, but he's quickly scooped up by a hero and deposited outside the danger zone.

It's been too long. Kacchans been struggling this whole time without stopping. Izuku was kept back by a small group of heroes while some helped civilians and ran damage control, but no one was actually doing anything. He heard Death Arms saying something about "Waiting for a hero with a better quirk" which was actual garbage. How did these people graduate? He waited for a real hero to do something, anything. Time came to a stop when he looked in Kacchan's eyes. So much fear. Before he registered what was happening, he was running. 'Why am I running?!' Realizing he doesn't have a plan, he starts thinking in overdrive. 'Ok, I can't legally use my quirk, so think. How can I get that thing off Kacchan? Page 25!'
He takes off his backpack and flings it into the sludge villain's eye, disorienting him enough fjr Kacchan to suck in a few desperate lungfuls of air. "What are you doing you damned nerd? Get out of here!"
Izuku shakes his head while trying to claw his friend from the villain's wet grasp. "Screw that noise! You're not dying until we become heroes, you hear me?"

"You little brat!" The villain rises up, threatening to engulf Izuku along with his initial victim. Before he could, however, a boisterous laugh echoes in the area. "Worry not, citizens, for I am here!" The blonde hero grabs the duo before letting loose a powerful punch. "Detroit smash!" The resulting air pressure splatters the villain across the street and parts the cloud above them. It starts raining, gaining admiration from bystanders.

Izuku was currently being berated by the group of heroes. "You could have gotten yourself killed kid, what were you thinking?"
"That was really dangerous, leave it to the pros."
It went on like this for a while. It doesn't matter though. He had nothing to prove to these people. He left soon after, leaving Kacchan at the mercy of various low-level heroes and blood thirsty reporters. The look on his face as he saw a smirking Izuku walk away was priceless. A skeletal man in baggy clothes runs in front of him, coughing up blood. "Wait!" The man regains his breath, hand on his knees before pulling out an ID. "I'm Toshinori Yagi, All Might's manager. He has an offer for you."