What if Harry’s magic had presented itself a bit more obviously when he was younger. Young Lily and Snape, for example, were able to purposely manipulate magic to make flowers grow, things like that.
What if little Harry discovered he could do such things.
What if little Harry were playing with magic happily in a park one day, only to be found by Dudley and his gang. What if they beat him so fiercely he was too terrified to used magic again. Except it kept building inside him, and he couldn’t control when it would burst out.
What if Harry became just like Ariana.
What if Dumbledore failed again.