1) Watchmen: Rorschach is framed in a much more positive light here, whereas in the book, neither he nor Ozymandias were really framed as entirely good or evil. This can be chalked up to Zack Snyder agreeing with many of Rorshach's views, so of course he would portray him in a positive light.

2) Hercules: Hercules in the myths was much more of a violent hothead, while Hades is actually one of the more chill gods, as he doesn't go around raping women willy-nilly like his two brothers. The only real bad thing he does is kidnapping Persephone, which is small potatoes compared to the actions of other gods. Plus, the only interaction he and Hercules had in the myths was fairly pleasant, with the real villain of Hercules' story being Hera.

3) Middle School: The Worst Years of My Life: Rafe in the book was much more of a troublemaker for the hell of it, rather than out of some noble desire to stand up to a tyrant running the school. Principal Dwight, likewise, while strict in the book, never did anything outright illegal like destroying students' property, rigging a state test in his school's favor, and framing a teacher he didn't like of a crime so that he could fire said teacher, all of which he did in the movie (this is one of the times I feel this trope worked for the best, because I found Rafe much more likeable in the movie, as he was, to be honest, a complete shit in the book).

(Mixed trope) The adaptation makes the protagonist unambiguously good and the antagonist unambiguously evil, whereas it was more morally gray in the source material.