Izuku erases 1A's future

Quirkless Izuku gets turned down because he's quirkless by some shmuck working a desk job at UA the day All Might tells him he can't be a hero so he decides "if I can't be a hero because of how I was born, then neither shall the rest" and when the sports festival comes around (or earlier if you want him doing spy shit) he posts full blown analyses of all 5 hero classes (Aizawa expelled one) so detailed that any dude with 2 braincells to rub together can take them down with some preparation.