As has been discussed in previous posts on this blog, the creation of your villain is as important as the creation of your main character/hero. And, just as your hero should have his finale, your villain should have the pay-off.
Once you've created a suitable villain, allowed him to rampage through the book/story, and nearly defeat your hero, it's time to unveil his ultimate defeat. But first you must ensure that this defeat connects sufficiently with your reader's automatic sense of justice.
No one likes to feel cheated. But especially so in a good story. A note to the wise:
The last thing a reader remembers is the end.
If your end lacks the punch and pizazz that you've built up throughout your story, a reader tends to feel cheated, deflated, and with a bad taste in their mouth. This also holds for the "end" of a character arc, including your villains' own.
Here's an example.The movie Indiana Jones and the Temple of Doom.
How would you feel if the leader of the cult, rather than falling to his death among the crocodiles, climbed up the ladder and was taken away by local police? Would you feel cheated?
Because after the build-up of how awful and terrible that villain was, you want him to die, and you want him to die in a way that is equal to the pain and suffering he has caused.
That's because of most people's inborn sense of justice. When most people were toddlers, and someone took your toy, you took it back. When they bit you, you bit back.
Though we know that's not true in real life, in books, most people wish to see equal or even greater punishment fall on those who have done wrong.
Making your villain truly despicable, someone your readers can hate with as much vehemence as they love your hero, is always a good idea. Just remember that when the end comes, when you finally have your villain face his/her defeat, that the pay-off is just as terrible as the build-up you've created.