What if, instead of what did happen in their fight against All Might, Katsuki called Izuku out for his attitude towards the unbeatable.
KNRKBR
Katsuki could feel his eye twitching. After years of this fucker lying to him and then giving some bullshit excuse that he inherited his quirk from All Might, now he's trying to sabatoge their fucking final.
"If you can't bother to fight him, drop out! Why would you bother trying to be a hero when you can't even pretend to fight a villain! Run if you want. He'll just catch you. I'm going to try and win. Like a hero!" Katsuki's voice cracked as he yelled at someone who was his friend, who he became a bully to. "A hero tries to win no matter what. Regardless of their opponent. Regardless of the potential outcome. If you think All Might is impossible to beat, you'll fail with any villain you think might possibly be stronger than you. I told you not to bother applying to this school for more than one reason. For all your analytics, you never seem to understand the fundamental truth of heroism."
"What's that?" Deku, despite all the violence Katsuki directs at him, is still curious and ready to learn.
"A good hero fights against the odds. A real hero makes the odds unimportant. If you think the odds are against you and you leave because you don't want to lose?" The blond let out a cheerless laugh. "You don't deserve to call yourself a hero!"
Katsuki yelled the last while flinging himself up and over All Might's Texas Smash that was launched.
As the fight started to escalate, Deku watched as Katsuki fought with his all, even though it was only a final. What he saw made his heart hurt. Kacchan wasn't winning. He might not be failing yet, but he wasn't going to win this way.
When Kacchan got launched again, Deku grabbed and hid in an alleyway so they could catch their breath.
"You're right. Just because he's my idol and just because he gave me his power doesn't mean he's unstoppable," Izuku's head was down. "While we can fight and give a good run, something a real hero also needs to know is when they're outmatched. We are, but not as badly as I thought. Do you want to cuff him or get through the gate?" There was a fire in his green eyes that wasn't there at the start.
Again with that damn quirk inheritance thing. Dammit, Kacchan looked at his hands and gauntlets. There were small blisters forming already and the gauntlets seemed to be at max capacity for storing his sweat.
"We fight until one of us can escape. Here, take my left gauntlet," he passed the heavy piece of equipment to his main annoyance. "You have a couple ways of using this. Pull the grenade pin to let it all blast. On the inside there's a trigger by your index finger. Pull that to let off small blasts like flash bangs." Here, he turned over the gauntlet. "There's also a lever you can pull here, on the underside. It lets off three blasts at a time in quick succession. You can use the trigger or the lever multiple times, it varies for each, or the big blast once. Use them at your discretion in this fight. Let's go."
He stood up on sightly shaky legs.
Izuku opened his mouth to ask if he was okay but decided against it. "Okay. Let's go Kacchan."
They turned back to the Main Street and kept the damage as close to the main wreckage as they could.
It ended up that, while they didn't beat All Might completely, they did well enough in their attacks that he was much slower. When Katsuki got hurt, Deku ran and grabbed him before going back to the escape gate despite his own injuries. While it didn't magically fix their relationship, it started the process to at least open a dialogue between them.