With the thread title being what it is that spoiler alert seems a bit pointless considering you mention the character's name! I always thought one of the best things about Lost was their willingness to kill people off. It can be infuriating to see a favoured character killed off, but if it's something that works well within the plot I can accept it.

(SPOILER)Nate's death in Six Feet Under was very sad - and though it's a film, let's not get started about (SPOILER)Wash in Serenity!