I have read this book at least six times, and there is one thing that sticks with me as a plot-hole: the Triwizard Cup as a Portkey. Barty Crouch Jr.'s intentions are to get Harry into the graveyard on the night that Voldemort is ready to regain "human" form. He intends to do this by having Harry touch the Cup first and be transported. This is essentially what he did:
-Kidnapped Mad-Eye Moody and kept him alive for months, while constantly brewing fresh Polyjuice Potion for his transformation
-Bewitched the Goblet to choose Harry as a champion
-Showed Harry the dragons, along with some help from the Weasleys and Hagrid
-Told Harry to use his broom to retrieve the egg, even though Harry's life would be at risk fighting a dragon
I didn't find the right solution from the Internet.