I'm wondering what you guys thing were the top saddest moments in the Lost series. For me, it goes: 1) The end of "The Candidate" from when Sayid grabs the bomb to when it shows MiB's face again (then my sorrow becomes blinding rage) 2) The end of "The End", where Jack died, Jack realizes he is dead while talkinig to his father, and the people in the church start hugging 3) Charlie's death, which includes him actually dying, when Desmond tells Hurley, and especially when Hurley tells Claire. 4) If you rewatch "The End", then any time a character "wakes up" in the flash sideways. 5) When Juliet falls down the hole in "The Incident". 6) When Locke finds out his kidney was stolen by his dad. 7) When Sun screams after the freighter explodes.
There are a lot more (pretty much any time anyone is mourning over a dead person or is giving a speech at their funeral, and when Hurley finds out Jack doesn't plan on coming back out of The Source after plugging it back in). For me, a lot of deaths were kind of ruined by how surprising their deaths were, like John's death. Locke is my favorite character, but I felt almost nothing when I saw him dead, first off because it was surprising and second off because I thought he was alive again. Sayid's death would not have been very sad if he didn't go down with the Kwons. If he had just blown up, it would have just been surprising instead of mournful. Ana Lucia and Libby's deaths were too shocking to mourn (though I felt very sad afterwards).
My final thing to say is it is very sad to watch the part of "Exodus" when everyone is getting on the plane and Life and Death is playing. I thought of how they all end up, and it made my eyes water.