It should have ended at part 2s final scene. They hit the third act and needlessly continued on and on and on.
Part 3 was random personality shifts that made no sense. And it's end was left with no resolution. No explanation of why any of that happened. And a sad excuse for Snow to end up how he is in the main trilogy.
I have never been so bored. I wanted to walk out and I have only done that once before in my life.