Bullies are persons who uses strength or power to harm or intimidate those who are weaker.
Bullies are characters who like to pick on others, especially those they see as weaker than themselves - bullying can vary in intensity from childhood pranks, stealing lunch money and name-calling to physical or emotional abuse (Like Bonfilia Meratti and The Harlequins in Good Wolf). Extreme examples of bullying can push a character beyond the classification of a mere "bully" and into the realm of being an "Abuser". All of them have insecurities which they want to push off onto weaker people. The reason being is they think they are important enough to be as nasty as they want to whoever they want but will normally respond with an almost insane rush of hostility to anyone who is obnoxious to them in retaliation to their nasty behavior.
Note: Make sure that the villain fits as a bully before adding here. Psychopaths and sociopaths don't count.