This one will be controversial in all likelihood but I do believe it.
At some point in 1998 Owen Hart was presented with a storyline where he have an affair with Debra, Owen turned it down, this lead to him becoming the Blue Blazer which lead to his death in 1999.
He should have done the affair storyline with Debra because it would have saved his life.
He would not have become the Blue Blazer, he would not have been put up on the catwalk and therefore would not have fallen.
Doing that storyline would have saved his life and he'd likely still be here today.
I know the response will be that his wife would have seen it but it's not real and she knows that, she has to she married into the Hart family.