King Leck in the Graceling Realm series (which I would only recommend with caveats for content, unfortunately XP) is great because he’s actually intimidating. He’s a genuine threat to the protagonist. Plus he’s just scary. It’s freaky what he finds fascinating. He’s definitely a psychopath. So he’s well-done and easy to hate because he’s actually scary and dangerous.
Damien Dahrk (not sure about that spelling, but it’s close) from Arrow is fun for his sense of humor. He’s a personable villain. And I like Loki for similar reasons. Charming villains are fun to love and hate.
And both Damien and Loki also have people they care about. If I recall correctly (it’s been a really long time and I didn’t watch Arrow much), Damien has a daughter that he’d do anything to take care of. And Loki, of course, cares about and wants to impress/connect with Thor. Connections are another thing that make villains feel human. (If you want a human-feeling villain. Leck worked for his lack of empathy/human connection, so it depends on what you’re going for.)
I don’t know if this is helpful, but I wrote a blog post a while back about traits that help flesh out antagonists and connect them with the reader. (If it’s not helpful/not what you’re looking for, feel free to just ignore it. 🙂 )
Speculative fiction author. Mythology nerd. Worldbuilding enthusiast. Singer. Fan of classic literature.