A villain is essentially the antithesis of the hero. His goals, values and behavior are generally opposite to what the hero would do. Once you have defined your hero, determine what he thinks he would never do, and these are the characteristics and behaviors your villain should possess. If your hero is an upstanding citizen, have your villain flout authority. If the hero protects children or old women, have your villain intentionally hurt them, so the hero can do what you designed him to do.
Villains are always as committed to achieving their goals as are heroes. They are motivated by the same passions as the hero. They feel the same emotions -- love, envy, fear, greed, pride -- but from their own perspective with their motivations being completely clear and understandable. Regardless of the goal of the villain, he is thoroughly determined to achieve those goals and becomes tougher and stronger with each setback. He embodies what scares and horrifies the hero most and is obsessed with achieving his goals.
Villains are generally skillful at what they do. They are smart enough to avoid making blatant mistakes, and they are good at lying and acting as though they are innocent. Villains are generally courageous and intelligent and able to disguise their behavior or intentions. A worthy villain is a good opponent and an expert at what he is trying to accomplish. If the hero wants to protect his crops from free-range cattle, the villain may try to get statutes passed to outlaw fencing or use other persuasive means to achieve his goals.
A villain is the antagonist to the hero protagonist. His role is to prevent the hero from achieving his goal, usually to the villain's benefit. He will cause trouble for the hero to keep the hero from succeeding, with no damage or danger being too severe to make him stop. He may appear completely ordinary, believe what he is doing is right and feel no guilt for any activity he does to thwart the hero. The conflict between the hero and the villain produces uncertainty and suspense, essential ingredients in the best stories.