Thread by @Massawyrm

For audiences, kindness and a moral center are assumed traits. You never have to explain motivations for unselfish acts. This is especially important to remember when writing antagonists. No matter how brutal the villain, they can still be kind to others, even amid villainy.

This is extremely helpful when trying to flesh a villain out. The cheap way to add depth to them is to give them a dog or a sick relative.

But you can have them show a moment of kindness, even to a foe - showing pity, remorse, or empathy - without having to explain exactly why.

Audiences innately believe in redemption and goodness, so take advantage of that and show a moment or two of humanity with your villains, and they will feel far more three dimensional - the goodness within them at conflict with their greed, anger, or hatred.

Of course, the common wisdom is that "A villain never believes they are the villain of the story." A villain may use that kindness, empathy, or the positive end results of their machinations to justify to themselves how they aren't so bad after all.

See: Thanos.

Also, giving them a line they won't cross makes them inherently interesting. A villain who is willing to commit one atrocity but not another tells us they have some sort of moral code ticking down there, instantly making them far more fascinating.