Sure, Trump hates to be humiliated or embarrassed, most people do, but with him it goes much further than that. Trump is a very narcissistic person. He can't handle criticism or defeat, so he will most likely not accept the result, I agree. The question is whether it's enough for Trump narcissism to just blame his defeat on the election by mail or whether he's going to do more.
Because Trump is not the kind of person that make strategic decisions, he will most likely just give it a try. That's what he always does when he wants to figure out what his supporters want. I don't know who this try will look like but It's certainly worrying when you consider how many weapons people have stashed away in their homes and that Trump's private police force is practicing right now how to hit civilians.