The Rambo franchise turned Rambo: First Blood’s complex lead character into a gung-ho action hero, but the gradual downfall of the series was set up by the first movie's changes to the source novel. In the closing moments of Rambo: First Blood, John Rambo tearfully recounted the ordeals he endured during his part in America’s invasion of Vietnam. After breaking down about his mistreatment, he surrendered and was comforted by his former commanding officer. The last scene of Rambo: Last Blood, however, saw the same character cut open a human trafficker’s chest, ripped out the man’s still-beating heart with his bare hands, and showed it to him.

https://screenrant.com/rambo-sequel-heroic-problem-book-changes-worse/