John wrote about two men in his third epistle: Gaius and Diotrephes.
Gaius was a man that helped Christians to grow in Christ.
Diotrephes set out to promote himself, not caring what happened to the Christians around him. He even went as far as casting them out of the church.
John ends his letter on this note: follow the good example, not the bad.
Christian, be a help to those around you, not a hindrance.