Villains are problematic not only in that they are usually the more proactive character, while the hero is reactive, but also because they are often doing the more interesting stuff, moving the story forward. I have many times found myself sympathizing with the villain just because I want to see what happens when they complete their plan.
If you want your reader to despise your villain, then they have to cause personal pain or trouble to the hero. Abstract villainy is not enough. I don’t care if the villain is killing millions of nameless people to complete his goal–they aren’t real people, this is fiction everybody!–but if he is impeding the hero in a specific, personal way, or causing her pain in a specific, personal way, then I feel more anger and frustration toward him than I would if he was the most evil character in the world on a global scale. The personal is what matters.
An example. The book I’m reading now, Wild Seed, had the potential to have a villain I was more interested in than the hero. He is an immortal that spends his long life breeding people for special powers, deciding how many children they have and with who. Some of them he breeds to ‘feed’ on with his own special power that keeps him alive.
This is pretty disgusting. But, it’s also an interesting idea. I want to see where his breeding program goes, how it works, and so on. They aren’t real people after all, it’s just words on paper, and I, the curious reader, want to see what happens. I expect that the hero is going to try to stop him, and it will frustrate me cause I don’t get to see the interesting stuff he’s doing.
The villain makes our hero part of his breeding program, tells her who to sleep with, who to have children with. Threatens her, and her existing children with death if she doesn’t obey. Now I want her to stand up to this jerk and escape him. Now I’m cheering for her, whereas before, when it was just an abstract concept, I was more interested in the results of his experimenting. Now that it’s personal, screw him!
This is what makes a good villain–not some shadowy, far off figure that threatens the whole world, but an up close and personal person who affects the hero in an intimate way.
Give it a try if you find people liking your villain too much, I bet they won’t like him as much when he’s doing something personally terrible to your hero!