What If?? (A Harry Potter AU Book)

So, recently I reread and rewatched all the Harry Potter books and movies and my mind is reeling with these scenarios of what could have happened if the story took this turn instead of the original plotline.

I'll be mentioning all possibilities of how the story would be woven if a particular incident took place. So basically, I'm trying to create multiple alternate universes which might in turn describe how significant a character was or how important was a particular incident and how it's not happening would have affected the future.

I'm sure you'll get to know wild crazy theories and I promise a lot of fun.