While I firmly believe that the Harry Potter films were the best possible adaptations of my favorite series that they could be, I do have a few issues with them. Aside from the tragic deaths that take place throughout the series (specifically the last two books) that I will never be okay with, characters were left out completely, conversations were altered and there were changes in how events (both major and minor) were carried out. In case you haven't read the books or seen the movies, there are plot spoilers ahead - read at your own risk. In no particular order, here are my main problems with the film series.
1. No Peeves.
Although he's a minor character that was always a major pain in the butt, he provided comedic relief (even after the tragedies in the Battle of Hogwarts) and gave the Weasley twins a run for their money. Also, he was a natural enemy of Filch, so he's basically a hero, right?
2. The reveal of the Half-Blood Prince.
In the book, the identity of the Half-Blood Prince was a big mystery and a major reveal. In the film, however, the Prince was mentioned in passing, and revealing of his identity was extremely subpar and overall disappointing.
Need I say more? 95 percent of the fandom is appalled at this change between book and film. "Did you put your name into the Goblet of Fire, Harry?" he asked calmly. However, in the film, Dumbledore is shouting and sprinting, beard flowing majestically as he tackles Harry. In the film, that was the real first task: surviving Dumbledore at that moment.
4.The missing humor.
Nobody can deny that, while extremely dark, the film adaptation of Harry Potter and the Half-Blood Prince was one of the funniest. In the books, Harry and the gang weren't humorless. It would have been nice to see some of those weird wizard jokes in the films.
The house-elf was strangely absent from the film version of the Goblet of Fire. While a small character, she played a large role in the events of the Triwizard Tournament. Maybe adding her story into the mix would have increased S.P.E.W. membership.
6. Voldemort's death.
In the books, Voldemort - when he finally kicked the bucket - had a very human death. There was a finality and a sense of closure in the fact that there was a body. There was tangible proof that Voldemort was finally gone; in the film adaptation, however, there was no body. Voldemort disintegrated in weird butterfly ashes, leaving nothing behind. Therefore, no closure, no hard proof that he was dead, once and for all.