Creating your antagonist is sometimes a lot more fun than developing the character whose role it is to bring the evildoer to justice.
However, if you want readers to be hooked in such a way that they will not only identify with the hero, but love to hate the villain, you must create an emotional response.
Readers read to form identification with the characters.
Identification is all about emotion.
The stronger the emotion, the stronger the hold you have on your readers.
An internal tug-of-war will produce intense emotions that readers may not understand intellectually.
Yet, emotions have nothing to do with logic.
They are the most powerful compelling force we, as humans, have.
If you create an opposition, and therefore a conflict, that causes strong emotions in your audience, you're halfway there.
You cannot do that by developing a character who inflicts evil for no other reason than frustrating the efforts of the main character.
He must have reasons and justifications for his actions.
These reasons must make sense to him in a way that your audience can understand.
This does not mean that readers will like the antagonist or agree with the pain he inflicts on others.
What it means is that they will see how he came to be the person he is.
If you wound him deeply enough, they may even pity him.
Give him a childhood where he was tortured or tormented so severely they can see the boy or girl cowering in fear.
Understanding the antagonist in such a way also makes for a more fearsome villain.
Think of the person who twists the bible to the point that he believes he is doing God's work by ridding the world of any particular group of people.
What is more chilling than being terrorized by someone who thinks he has God on his side? There are two ways you can develop a frightening opposition like this.
The first is to begin with a character fact list.
The list will contain the antagonist's physical description and his personality traits.
You would include any scars he might have as well as how he got them.
Also, add his quirks, idiosyncrasies, and distinctive speech patterns.
When you have completed the character fact list, you will write out his back-story.
The back-story is your opposition's history.
Here, you will note where and how he grew up.
You will also detail how many sisters and brothers he has, if any.
Everything of any importance, up until the story begins, should be noted here.
A great way to add further dimension, and get inside the antagonists skin, is to write a journal in his voice.
You will write in the first person, as if you were him.
One rule in this exercise is that the character must be completely honest.