Few movies actually make me think like that.
One of them was “The Man who Killed Hitler and Then the Bigfoot”
It’s a movie about the man who secretly assassinated Hitler, but both sides covered it up, and the war went on as if nothing happened. Nobody knew of his actions, and his life was ruined. He came to realize the futility of fighting since, so long as both sides wanted to fight, conflict would go on no matter what.