What movie ending made you cry the most?
For me, there are two: The Return of the King and Kong: Skull Island. I watched both movies in the last 4 days, and also watch the first two LOTR movies after Skull Island and before TROTK.
I'll give more attention to the last one because it depends less on the rest of movie itself than the ending of TROTK, which, despite being more emotional, is so because it is a farewell to a journey, both for the film's protagonists and for those who watched them.
On the other hand, the ending of Skull Island is almost completely independent of the rest of the movie. Of course, it's more beautiful when you've seen the movie, especially because of Gunpei's katana and the hot dog and cold beer while watching a Cubs game. But even so, you can show this scene to someone who hasn't seen the film and that person will perfectly understand the scene and what it means for the characters involved, and this without any speech other than the sports commentator saying that the impossible dream became the possible dream.