Bullies intimidate. They induce fear in others. They have to be more important than anyone else. Bullies make life miserable for their peers, but often behave in an ingratiating manner to their superiors. They cause eyes to roll and stomachs to clench. They don't share their knowledge and try to keep others from excelling or succeeding. If someone manages to squeak past and get noticed for great performance, the bully will find some way to get some credit for it. Either she trained the other person, gave them an idea, or somehow had a hand in whatever they did.
If you've ever worked with a bully, you know they're practically inescapable. They are everywhere and seem to have their nose in everyone's business. They'll be your friend to your face, but they'll quickly stab you in the back as soon as you turn it. No one is ever doing anything more important than they are, no one works as hard as they do, and they let everyone know the office would fall apart without them. They tend to put others on the spot and refuse to take no for an answer. If they are ever called on their behavior they will do whatever they can to divert attention away from what they've done and onto someone else. They are often so good at it that the other person will end up apologizing. They keep others from doing their best and stand in the way of progress.
Do you have a bully on your team? If you do I guarantee the morale of your staff is being lowered because of your bully. Here's what your staff is thinking: "Why does he let her away with it?" "Can't she see what's going on?" "I don't know how much longer I can stand working here." "There's go to be a better place to work that doesn't put up with this!" Bullies often appear to be your best employee, and they may be talented, but talent never makes a bully a worthwhile employee. Their ability to undermine, aggravate and insult others makes them a liability. You will see more easy-going staff leave because they just can't stand coming to work anymore. If you have a bully on your team, take it seriously. They generally don't change. Workplace bullying destroys drive, passion and confidence. If someone brings this post to you tomorrow, pay attention. It may just be their last attempt to get you to make a change that will make it possible for them to stay with you.