Bela Talbot - Supernatural
Bela was badass. Poor Sam and Dean never really had a chance against her wit and quick thinking. She was always one step ahead.
Serena Joy - The Handmaid's Tale
Serena's a pretty horrible person even under the circumstances, but she does play an interesting part on the series. You can't help but feel bad for at times, which just goes to show what a well-crafted character she is.
Regina Mills - Once Upon a Time
Regina had the best character development on Once Upon a Time. She went from being the evil queen to a woman who would put her life on the line to save her former enemies.
Mona Vanderwaal - Pretty Little Liars/The Perfectionists
Mona really was one of the best parts of Pretty Little Liars. You never knew if you were supposed to feel sorry for her or if she was playing the audience as much as she was playing her friends. We can't wait to see what The Perfectionists will bring for her.
Katherine Pierce - The Vampire Diaries
Katherine was the most hilarious villain in history. It was pretty much impossible to hate her. She was extremely smart, sarcastic, and was always one move ahead of everyone.
Reign - Supergirl
Reign was an amazing antagonist during Supergirl's third season. Sam's own strength mixed with Reign's evil desires created quite an interesting villain.