Well, here's the reality of it .... If the character has to die to make the plot move forward and to make this story incredible, then bite the bullet and do it. It's hard, we all cry, and then you do what you need to. It's like the first time we realize that one of our books just isn't going to make it through. Killing off our babies (books in this case - please don't suppose I am actually implying anything else) is hard, but we do what we have to in order to make stronger manuscripts and more solid, likable, and amazing characters - even if we make them die in the plot somewhere.
Killing off a character can do several things for a story. It can be the driving force for the hero/heroine, it can make the survival of others that much sweeter (say in a battle scene), or it can be the needed moment that allows the plot to proceed (as in a murder mystery - you can't have the mystery if there is no death of a character). But when an author builds up to that moment where you know someone must die (your are feeling for the characters, you are gripping your book so tight you knuckles turn white, and your heart is pounding as you try to determine who will survive, maybe even tearing up a bit) and the author denies you that moment, it's extremely disheartening. Especially if it is the climax of the story. Denying the reader that climax, that moment of truth, really will make or break a book for many. So yes, it's hard to kill off the characters. But ruining your story to save them all because you can't bring yourself to do it, is more likely to hurt your book than killing off the character would have hurt you.