If you're writing or outlining a horror, the chances that one or more characters eventually kick the bucket are pretty high. (Of course it isn't required for people to die if the book is a horror, but I'd estimate that in most cases it's quite likely.)
In the outlining/pre-planning stage, character deaths are easy to drop in. A decapitation here, a disembowelment there, a sickness or freak accident or simple case of being in the wrong place at the wrong time. Usually there are certain main characters that you already know will perish, and you can flesh out your plot a little bit by putting some thought into exactly how and why they they get the axe, whether figuratively or literally.
And when that happens, you will eventually be faced with an inevitable yet unexpectedly difficult task: killing off a character that you truly like.
It sounds obvious, but once the draft is going and you've gotten to really know these characters that you so easily threw under the bus in the brainstorming stage, things can get... confusing.
Should I really be doing this?
Should I change my original plan and let the character live, so that the readers don't hate me as much as they would if I carried this out?
Should I fluff up the death/take it "off screen"/make it more sudden and less descriptive than I planned so that it's easier to write?
Should I should I should I?
In short, I personally believe that the answer should be no in all cases. (Unless it will directly contribute to bettering the story as a whole, which is quite unlikely since you're only asking these questions to yourself in the first place because you're afraid, am I right?)
And rightly so. Because seriously guys, there's no way around it: writing the death of a quality, well-fleshed-out character that is incredibly likeable and bound to become a reader favorite can be quite traumatic, in multiple ways.
You almost feel like you're betraying them, which is silly because of course "they" don't even exist, yet there you are with this horrible pit in your stomach as you're writing about this girl laughing and enjoying a cold soda in the sun and you're like, enjoy that soda honey, you're not going to get many more, and then she mentions how she wants to be a veterinarian when she grows up and you're like okay I am just EVIL.
(And not the type of fun-evil that you feel when you write other scary scenes. You will feel bad, truly and deeply.)
And because of that, it becomes very easy to distance yourself from the character in your mind as you write the draft, knowing that they're going to die anyway, but I'm here to encourage you against making that mistake.
When you distance yourself from your characters, they lose life, and damn it if they aren't already "dead" by the time you kill them off anyway. The shell is empty, and therefore, so is the feeling of loss. It will give the death (and the story surrounding it) much less worth, it won't stir up any deep emotions, and at the end of the day, it'll just turn into another one of those horror experiences that rippled away into something bland and cliche.
Because in horror, almost everything is cliche. In order to make the readers not care about that, you need to get them invested. You need to endear them to your characters.
And, eventually, you need to horrify them.
That's why they're here, that's why you're here, and that's the goal always, isn't it? To tell a story that sends them away to sleep with the light on? As a general rule of thumb, I'd say that if you don't feel disturbed with the story yourself, you're probably doing something wrong.
A poorly executed death can turn a reader off in an instant. Of course, it always boils down to staying true to the story and the characters. Easier said than done, right?
(But you can do it. I promise.)
Until next time, stay spooky my friends!