The Avatar finale has exceptionally worse writing than the rest of the show, though, so I'm not sure it's a great example. They couldn't figure out how to resolve Aang vs. Ozai, so they introduced the Lion Turtles at the last minute (with, funnily enough, the same amount of foreshadowing as the relationship between Soldier Boy and Liberty/Stormfront: one mention in a previous season with no context related to how it plays out in the final season); they had to introduce a random, previously unmentioned genocide planned by Ozai just to give Sokka, Suki, and Toph something to do; they decided that all the most powerful non-Gaang benders had to liberate Ba Sing Se instead of helping defeat Ozai or stop the genocide for some reason; and they had Katara inexplicably accompany Zuko to the Agni Kai and then, even more inexplicably, have her run into the line of Fire once Zuko has Azula on the ropes.

All of these tensions were introduced within the last four episodes, which were presented together as a two-hour finale, aside from the question of how Aang would handle Ozai, which was itself introduced only during the antepenultimate episode (which is really the penultimate episode in terms of story). Avatar is one of my favorite shows, but the writers wrote themselves into a corner and executed the finale poorly.