10 Subplots That Saved Entire Movies
7. The Life Of Vitto Corleone - The Godfather Part II
Marlon Brando as Vitto Corleone in the first Godfather will always be a career defining icon, but the same can be said for Robert De Niro playing the same character but younger in The Godfather Part II through flashbacks that intercut throughout the story.
Now, Godfather II wouldn't be outright terrible if you cut these flashbacks out, but I guarantee you that it would not be the groundbreaking, seared into the face of film history for all time, influential classic that it is. The reason why is because this is one of the textbook examples of how subplots should always, ALWAYS act in support of the movie's central theme. That theme in this case being how power will always corrupt and ultimately destroy you in the end.
As Michael consolidates power in the present day, we flash back to Vitto rising to power within the ranks of the Corleone family. With these two stories working in conjunction, on top of the fate of Vitto in the previous film being so well known, it tells the audience what will eventually, inevitably, happen to Michael, by showing how Vitto started out, and the present day reminding us how he ended up.