The Godfather Trilogy, one of the most famous cases of forced sequels ever
Unnecessary sequel: A sequel (most often to a movie) that somehow insults or defames the original due to quality (or sometime retcons), or simply adds onto a completed story in a way that is simply not needed.
So, what exactly are the parameters for an unnecessary sequel? So far I’ve found a few different types.
1. It’s a rehash of the original, or simply a bad story. Ghostbusters II is my preferred of the two movies, but the cast is ashamed of it basically being the same plot as before. Pirates of the Caribbean: Dead Man’s Chest is considered a rehash of the original in terms of basic plot, but is still well liked due to the addition of interesting villains and action sequences that set it apart.
2. The sequel adds onto a completed story, and doesn’t lead to some sort of revelation or such. This is especially prevalent with completed franchises that had a “very freaking definitely the end” installment, only to get another sequel a few years later that serves little point other than “another adventure starring the hero, the comedic relief, and lacking the lancer and dark horse!” A good example of this is once again Pirates, with On Stranger Tides adding nothing to Jack’s difficulties with paying the debt of the Black Pearl / Will Smith’s character development, and aside from strong action sequences and magic, has rather lacking dialogue between anyone that isn’t Jack, Gibbs, and Barbossa. On the other hand, Harry Potter and the Cursed Child is set after the very final installment, and is simply interesting and well written enough to justify its own existence, and not all sequels of this kind are bad.
3. The studio mandated a sequel. The Godfather Trilogy is infamous with the second film being made because the film maker was desperate for money, and the third just to kill off the character.
4. The sequel makes a major retcon / makes the ending of the previous movie null. A good example is Star Wars: The Force Awakens. A lot of people liked the movie. Doesn't change the fact it made all the work that Luke did in the original trilogy literally pointless as the new First Order is even bigger, better, and ten times as vaguely evil as the Empire was, and is pretty set on making life even worse than under the Empire. Other cases are where sequels undo a character's death so they can show up again with little to no thought or consequences, thus making everything in the previous installment about the death just null. Or even worse are sequels that introduce franchise changing retcons that either make the previous installment flat out pointless or simply impossible in the new way the universe works.
So are some of these way too nit picky or specific to form a definite definition of what an unnecessary sequel is? Or is the definition required to be specific in what it does?