I think mine’s Z for Zachariah. The book is insane. A psychological survivalist thriller between a 14 year old girl and a strange man with unknown intent. The movie is… not this. They changed everything meaningful about the characters and lost all the tension. Hope someone does it properly one day. What’s your adaptation peeve?
Every Huckleberry Finn. The entire narrative is about Huck discovering his moral sense on his own and contrary to his community, and acting on it, all without realizing that that’s what he has done. The changes happen in his head and can’t be successfully documented with an on camera actor. First person narrative is where the greatness of the novel lives. Filming Huck’s adventures from a third person, external perspective can’t center that growth and discovery.