The ultimate, far-reaching, and all-encompassing question that everyone asks is "Why didn't you make a decision as to how to avenge your father?" The fact that Hamlet never makes up his mind as to whether he should do something and how to do it is his tragic flaw. The answer to this question would help to explain everything; and, had it been asked soon enough, Hamlet could have found a way to expose his uncle and mother in a way that would have been less fatal. He could have done so many things in response to his discovery that his mother and uncle killed his father. He could have left Denmark, gone back to school, and returned when his uncle died later. He could have eloped with Ophelia, too. But Hamlet became so consumed with indecision that he ruined any chance that he may have had to make peace with the situation.
Here is a list of possible questions for Hamlet:
Did you love Ophelia?
Did you love your uncle before he married your mother?
Why is revenge so important?
If you committed suicide how would your father's murder be revenged?
Did you want to be king?