Dark fantasy (and all dark fiction, for that matter) is a genre I love because it allows me to explore the various shades of moral grey. Instead of black and white (shining knights and cackling villains, heroic kings and evil viziers, noble warriors and cowardly evil wizards), dark fantasy deals with characters who are equal parts good and bad. There is less emphasis on "heroes" and "villains", but more on actions and consequences.
But an interesting article on Psychology Today gave me a bit of food for thought. The article says: "We rapidly learn not only about our heroes' shortcomings but also about the villains' humanity as well."
The truth is that every person is flawed. There is no such thing as "pure good" or "pure evil". In the end, people make the choices they make for a wide range of reasons.
That doesn't mean we should completely discard the concepts of "good" and "evil" completely. For example, the actions of the Nazis in World War II. All of the people who did those terrible things were fully human, and no doubt many of them had redeeming qualities that "showcased the humanity of the villain". But that shouldn't detract from just how terrible their actions were. All the horrors, torments, and suffering they inflicted on others isn't reduced just because of their humanity.
One of the dangers of complex villains is that we fail to take into account their villainous actions. If, by the end of our story, we start to sympathize or empathize with the villains, we stop taking into account their actions and start looking at their reasons. This can desensitize us to the horrors of their actions, and almost give them a justification. That is a VERY dangerous road to go down!
Think of all the school shootings that have occurred in the last year alone. I'm willing to bet MOST of the shooters had real "reasons" why they felt the way they did—everything from psychological disorders to abuse to trauma. But those reasons don't justify the actions. The things they did should NEVER have happened, no matter the reason.
Fiction that attempts to help us understand or sympathize with the villains can blind us to the villainy of their actions. That can be perilous in our modern world, one filled with so many shades of moral grey.
We still need the concepts of "good" and "evil", and we can still strive to reach one while avoiding the other. It's a much more complex world than black and white, but that doesn't mean we should stop seeing good and evil. If we get lost in the shades of moral grey, the world is doomed to be a dark, unpleasant place!