What great classic films should definitely never have a sequel?

Which classic films would genuinely NOT benefit from a sequel, and WHY? (Unless it’s obvious to all, might you tell us WHY you offer your answer?)

These days, many (almost all) movies are made with a sequel or trilogy in mind. Even if the story ends with the destruction of the galaxy, there’s always room for that follow-up (and the potential for additional ca$h).

In the past, movies were not created with this mindset. Which movies are notably Not sequel ready? In other words and in a roundabout way, how have sequels affected the quality of the movies being made today?

In my thinking, Groundhog Day is a good example. The story is completely wrapped up by the end. No sequel necessary or wanted.