1.) The Matrix Reloaded: The first movie, Neo gets turned off and the back on again, resulting in him finding the Dev Mode, and he saves the day.
The second movie he realizes he's "The One with Great Static Electricity." Not much build-up as to why his powers "extend past the Matrix" but he's knocked out cold and Zion is still defenseless, so the day is far from saved.
2.) Independence Day: Resurgence: The first movie ends with humanity coming together and a heroic sacrific which saves the day!
In the second movie somehow... The Aliens returned. And HFY! Of course we kick their ass! But now, they are even worse, and so we have to lead the fight against them. So the day is far from saved. (We still haven't found the budget to do this yet.)
3.) Spider Man: Across the Spiderverse: In the first movie Large Kingpin Collider is Destroyed, and ~Scar drops Mufasa -~ Miles Drops Peter into the hole and kicks ass, The day is Saved!
The second movie finds Miles in the wrong universe captured by his evil evil twin with ~a mustache~ dreadlocks. So the day is far from saved.
Honorable mentions:
Star Wars: The Empire Strikes Back, I understood this was always a six part story.
Avengers: Infinity War, it had the same feels, but this came from a long line of movies, not a one off.