I admit The Vampire Diaries (TVD) is one of my favorite shows on television. Why? Because the writers know what they are doing.
Just one of the impressive things is watching the writers create three dimensional villains. The villains are not just "after" the heroine/hero. There's a real purpose with relatable motivations. Damon was determined to be reunited with the person he thought was his true love. Katherine sought to bargain for her freedom (while staying alive!) after being in hiding/on the run for 500 years. Klaus wanted to become the unstoppable hybrid and create his own bloodline (family) because he felt rejected and unloved by his own family. Though these characters are ruthless and do unthinkable things to accomplish their goals (and are all about retribution), the writers also ensure that the audience sees their vulnerability and understands their motivations. By doing so, the "villains" have become fan favorites. Fans want to see them happy, even though they have done horrible things and their actions often conflict with the best interests of the heroine/hero.
What book, television show, or movie do you think created a villain done right?