A friend, looking at a synopsis of mine, was horrified to see I killed a particular character in the first 15 pages or so.
"She's such a great character! You're not using her potential!"
The character did, indeed, have a lot of potential. So do a lot of people who die "before their time." While I've come a long way from being entirely a "seat of the pants" writer--shoot, I'm feeling downright nervous that I don't know the endgame for Loki or Coyote in my NaNoWriMo novel!--I still don't engineer a plot or a character.
I see plenty of blog posts about how to incorporate flaws into characters or how to create complications for a plot… and I feel relieved that I can just pass by them. My characters come to me fully formed, with plenty of flaws intact, and they have their own plans with what will happen with any plot I create.
Not to say I do no engineering. I compare my writing to gaming because I will create a plot and a series of potential problems and I have some outcome in mind. I have a complex world that I've engineered in my head that has its own laws. However, my characters will do what they will. I can rein them in some by creating (hopefully logical) consequences for their action based on the laws of the world I've created.
Sometimes those consequences are that characters die. I give my characters free will, just as any human ought to have.
Because they are people. They - the characters, not the whole novels - are my children. Each have pieces of me… combined with pieces of other people I've met, or seen, or read about… and given a spark of will. The character, whether he or she or it be an adult or child, is the summation of many parts, a synthesis and a synergetic being.
While I create the world and the original problem, most of my writing is listening to my characters and transcribing. They tell me what they will do in these situations. They don't always tell me why, but eventually I figure it out (or, I have so far… like I said, these Tricksters have me in a bit of a tizzy). It's not me moving them around like chess pieces, it's me interacting with them as persons.
I've mentioned a few friends I have who do far more engineering. Their outlines are huge and detailed… they ask me for my thoughts on something, and my answer is not helpful because I ask what would be the most likely thing the characters involved would do. They make their characters do stuff; their characters serve their plan. Plenty of good stories are written like this--just not by me.
My stories are archives of my characters' lives. Once I discover how things go, I can't change the plot or the motivation. I can adjust what I include in a story--and what you include or omit can make big differences!--but I know what happened and what will happen. Not because I created it, but because I'm an omnipresent being in my characters' lives… and it's my job to tell their stories as truly as I can.
Even if they die in the first few pages. It would dishonor their story to change it just because it's unfair or a waste.