To Illustrate this point, two not current but not old great films will be used: Children of Men (2006) and Michael Clayton (2007). Both have well developed plots. “Children” is heavy on the futuristic action/adventure with lots of intrigue and double cross, while “Clayton” takes on the legal thriller genre. Both male protagonists start out as hard boiled cynical characters who see no merit in what they're doing or where they're at personally, but they change completely by the final act.
Some Points on Character Arc and Plot Development
Plot development is obvious to most. A standard movie script is usually in three parts or acts. The opening to introduce the characters and the situations. The second usually involves an event that changes everything or demands a new solution. That event in the second act is known as the plot point. Things usually change from that point. And of course the third is the pursuit of resolution, hopefully, that makes sense and ties all loose ends.
A really good character arc flows along with or on that pattern also. Someone upset in the opening scenes over his wife's murder and deciding on revenge is not a character arc. It takes most of the movie to get that fully if it is done well, and it becomes most apparent in or by the third act. The character begins with a certain weaknesses or strengths, runs into an episode, usually around that plot point in the second act, that stirs something within him or her, forcing an attitude change that often results in a life change in the character's essential being by the story's conclusion.