(Beware of trigger words. And remember this is a rant about literature and storytelling before you throw stones at me.)
I just started to play an awesome game that got spoiled by one single scene: the hero was imprisoned and tortured. Ouch.
Not that I could be chased off by a torture scene. It was even staged visually good and not ugly. Still, it turned into a big immersion breaker for me: there was no sense in the inflicted cruelty. I remember similar scenes in other games, and more in movies and books, all of them cruelty without a in-world reason. Oooh, it's a prison, let's add some torture to show how evil the bad guys are!
This is crap. Utterly crap. And the worst part is that people read or watch these scenes and don't ever think about the bad guy's reason to do this ... and, as this reason is missing, they care even less about what it means for the victims. Almost all media show this the same way far too often, which leads to rather unpleasant conditioning. I can understand that nobody wants to think about pain and panic and being utterly helpless when they enjoy a book or movie. But a writer has to do. Cruelty without reason is stupid and has no place in a good story. It can even easily spoil the experience.
Your audience will likely not ponder the reasons actively - at least if the scene is solid. But in any case, they will feel the impact of reliable research behind the character's psyche.
Please note that this rant is not about horror stuff like Saw, but about scenes like Theon at the Dreadfort in A Game of Thrones, which is a great example that works at all levels. This is about a Fate Worse Than Death. (Link to TVtropes is added below. I want you to read on, not stumble through the maze of tropes for the next two days.)
There are reasons why humans torment their own kind. Some want to get information, some want to break their victim until they confess a pact with the devil. And that does not even include the perpetrators for whom an author's research should delve into forensic psychology.
When I did research about 16th century jurisprudence and its dark parts, I went to a ... no, not a shrink, but to psychology-savvy people whom I could ask about one of the most detestable things people do to each other. What drives people to torture others? What enables them to do, especially those who get drunk afterwards and want to forget? Why do some even have fun? What makes Guantanamo happen? This research was one of the hardest I ever did, due to the delicate topic, the loads of stereotypes and twisted pseudohistorical facts everywhere. It is also impossible to show the whole picture by facts only. So I read transscriptions of secret letters from Early Modern prisons, protocols, executioner's diaries, and put a psychologist or two to the question about psychotraumatology. Of course this workload was meant for a novel plot and not for one scene only, but even a small research for the basics will take some time.
Before you write a scene including torture and other cruelty, do four things:
First, if you have written but one word of that scene already without research, lock it away.
Second, do the research. Make sure you don't puke on your keyboard.
Third, ask yourself if you need the cruel scene.
Last, put morality in the trash can. Think like the villain.
This is most important even when you intend to write the final scene from the victim's point of view. The victim most likely does not know the villains motives, and definitely not what the villain feels while doing villaineous things. You, as the author, have to know, to write a consistent and completely believeable scene.
There's only one issue about ethics I want to add: Innummerable children, women and men suffered and still suffer from their own kind all over the world. I would feel like a traitor if I used cruelty in stories just like a cheap show effect. Whatever we see and read in the media influences us.
Think about the one single bullet that blows up a car. Spectacular nonsense, yet people expect it. Many of the current show-effect torture scenes in movies, games and books partially derive from this backlash: for whatever reason, sometimes authors rely on other fictional sources instead of solid reserach. I understand time pressure or lack of money, but that's only a reason, not an excuse.
Turning torture, warfare, rape, and other traumatic incidents into bad stereotypes will not help our society to consider these topics in all their facets and their full impact on the human mind. I want my readers to get a glimpse on what cruelty really means, and maybe even think about the fact that reality is, unfortunately, always one step ahead of fiction. No morality there. And don't tell me that understanding the villain makes the scene less evil for victim and audience ... this works out the other way round, as plausible motives for the villain use to do.
Now is that too tough on the audience? Some time ago I read a review on a fact-based historical novel about a witch hunt, written for teens, in which the questioning scene was called so cruel that a worrying mom who read it felt sick. The scene was simply believeable, not overly direct and cruel, and hey ... wouldn't you feel worse than sick when your fingers were stuck in thumb screws?
This is what immersion feels like. Ouch.
Now you may be off to the flypaper of tropes. :)
TVtropes: Fate Worse Than Death