The evil antagonist is the one who is evil for the sake of being evil. This character may have a back-story that gives them some excuse, but generally it’s not critical to understand their why. All that matters is how they satisfy their greed, hunger for power and uncompromising drive to achieve their nefarious goal at any cost, and how they torment the hero of the story along the way.
Often, we feel nothing but hatred for this character, they represent the worst traits of humanity distilled and concentrated for effect. No-one feels empathy with the likes of Lord Voldemort from Harry Potter, Sauron in Lord of the Rings, Darth Sidious in Star Wars, or Doctor Smith in the revamped Lost in Space. They have no redeeming features.
But there is another kind of evil antagonist—the trickster. They’re usually a secondary antagonist to some greater evil, either facilitating the main antagonist, or confounding the hero for their own means. Yes, they’re evil, but they have moments of vulnerability that fool not only the hero, but us as well, into empathy. We can almost see ourselves in their place, even if just for a moment.
My favourite examples of the trickster are The Master/Missy from Doctor Who, Loki in all his incarnations, Moriarty from Sherlock Holmes and, most recently, Ms Wardwell (otherwise known as Lilith or Madam Satan) who was the sole reason I watched the entire first season of the Chilling Adventures of Sabrina in one sitting!
Of all the antagonists I adore tricksters above all others! What I love most about these characters is their intelligence and wit. So, it’s really no surprise that I’m incorporating one into my current work in progress (known for now as ‘The Japanese Story’). My trickster is a white fox who acts as a messenger between humans and Gods. He’s a fun character to write and I hope I do him justice as his role develops.