I have started working on my dark fantasy project and I have been thinking about general war crimes ect. I have written dark subject matter before but i'll just say this involves a sacking/raiding. Anyway whats the best way to approach ruthless brutal behavior in characters?
My current MC is a mercenary for hire who murders with zero remorse, having such a character as a protag definitely spices up writing about them because they don't have to adhere to justice
. I don't know that there is a best way. It all depends on how you want your readers to react. Do you want to spell it out for them and perhaps leave little to the imagination yet have great shock value? Or hint at the terror and let the reader fill in the details? And what about pace of the action? The hordes came sooner than expected, blade after blade slashing open every pregnant belly, spilling the contents into the dust whilst the men were forced to stand and watch... Here you tell the reader what's happened, and they react with shock/horror/repulsion. The hordes came sooner than expected, their gruesome legacy a blood-soaked earth of human misery... Here they use their fertile imagination, and will see in their own minds perhaps something even the writer couldn't envisage. It's about working out what you want to achieve in the reader. Hope that's of some help.
The scary thing to find out about atrocities, in my opinion, is how little distance there is between "regular people" and the circumstances or changes it would take for the majority to commit terrible atrocities. They need some way to live with or justify their actions. "Just doing my job" / "Just following orders" - moving responsibility from themselves to authority "The scumbags deserve it" - moving responsibility from themselves to their victims "I'm better than them" - the victims were of no consequence, it didn't matter what happened to them anyway "If it wasn't me doing this, then someone else would be" etc. etc. Not to say you don't get people who are more easily defined as evil and love committing atrocities, for more complicated reasons, but historically most people who commit atrocities are pretty much like you and me. With that in mind, how you describe such actions depends very much on the point of view you're telling them from - victim, perpetrator or observer.
If the tone of the book is intended to be overall dark, then i believe you would have to be somewhat gruesome in your descriptions. Swampdog's first example is a great one and it still is not too gruesome. If you read Brent Weeks's The Night Angel trilogy, there are some descriptions in there that make one's spine tingle, but it is written well enough to be regular fantasy overall without being too dark.
If you want to maximize the reader's revulsion, focus on the impact on people affected by the character's actions.
