I have 2 favorite types of villains in books. Those that change, and those that are convinced they are the hero.
So - Numero uno: Villains that change. Two of my favorite baddies are from even the same subgenre: Christmas.
Mr. Grinch is decidedly a villain to begin with. He steals Christmas. What could be worse?
And while Ebenezer Scrooge doesn't hasn't stolen Christmas, there's a reason why both "Grinch" and "Scrooge" have been used as appelations for those who have decidedly sour dispositions at Christmastime. BUT - both of these characters also have the benefit of some enormous character growth in a comparably short amount of time relative to the rest of their days. And That is why I love them so much. They go from despicable, ornery, grumpy individuals to those who decide to join in the festivites and have a complete change of heart. There's also a reason I read both of them every year to my family.
My other favorite type of Villain from books I read as a kid - and still in books I read
now - are characters like Grand Admiral Thrawn and Joruus C'baoth from Timothy Zahn's brilliant Star Wars Trilogy consisting of Heir to the Empire, Dark Force Rising, and The Last Command. These are villains who see themselves as the hero, or are put in the villain role not based on their villainy, but rather because that was just the side that fate put them on. They view themselves as principled and tend to view things in a more "grand scheme of things" kind of role. These are also the villains who often - like Javert - eventually face a crisis of conscience that just doesn't quite compute, leading to a mental breakdown, madness, & them sometimes deciding to embrace more traditional "villainy," or as with Javert - death.
In a recent book that I narrated, Jenelle Schmidt's Second Son, also has a villain who falls into this category. I loved voicing him. If you haven't checked it out, the series is among my VERY favorite I've narrated.
Those are my favorite literary villains. Honorable mention from TV & the annals of Star Trek:
