Times an actor used their clout to change a movie
Although the actors are what get the most attention, at the end of the day the directors, writers, producers, and executives are the ones who are supposed to determine what happens in the story and what characters do. If an actor doesn't like the direction their character is being taken in, it's usually out of their hands, they're contractually obligated to do the work. Or at least that's the case for most actors, if an actor is popular enough and a huge box office draw, then their ideas are more likely to be taken to be implemented in order to stay in their good graces/not piss them off.
Marlon Brando was infamous for this, he was such a popular actor, that he could get away with doing whatever the fuck he wanted and the crew had to take his ideas seriously or risk him just walking away. The Island of Dr. Moreau is one of the most notable examples.
And then there's the well-known trend of big action star actors having it in their contract that their characters can't lose a fight, like with Dwayne Johnson or Vin Diesel.
So what other actors have used their clout to change movies to be more like what they want?