The Quidditch World Cup being cut right as it was starting always felt so abrupt and anticlimactic. Of these options, it's the most disappointing for me.
The omission that bothers me the most, however, is the lack of Barty Crouch Jr.'s backstory. With no real context, he just kind of comes across as a crazed psychopath or something; we don't get any real information on the circumstances surrounding his deeply troubled relationship with his father, and his motivations that led him to join the Death Eaters and feel such a loyalty to Voldemort.