Jezebel was about as mean a person as you can find. She put out a contract on Naboth and had him killed just to use his vineyard as a vegetable garden for her husband, Ahab. As the king of Israel, Ahab could have had a hundred vegetable gardens, but he wanted the spot Naboth owned because it was convenient. So, Jezebel had Naboth murdered for nothing more than convenience.
When we see people like Jezebel, our first reaction is to wonder how a person could be so mean. We presume we are not like that, yet the fact is: we all have a Jezebel inside us. But for God's grace, we'd do the same or worse than Jezebel. We should first react to a Jezebel by getting the plank of sin out of our own eyes (Mt 7:5).
Often, our next reaction to the Jezebels in our world is what we call "defense." We reason that if some people are going to be so vicious, we must protect and defend ourselves. However, Elijah's reaction to Jezebel was not defense, but prophecy (see 1 Kgs 21:17ff) and discipleship. He finally defeated Jezebel and Ahab by making Elisha his disciple and by anointing Hazael and Jehu through Elisha and his disciples (1 Kgs 19:15-17).
In summary, when we see mean and vicious people, our reaction should be repentance, prophecy, and discipleship.