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?
The Dark Tower. Eragon (but the books weren’t great anyway). Where the Wild Things Are. The Lorax. The Cat in the Hat. How the Grinch Stole Christmas. The Shining. Several versions of A Christmas Carol. King Soloman’s Mines.