Impmon

Impmon is a Digimon without a Tamer who is living in the human world. He is selfish, cocky, greedy, loud-mouthed and aggressive and love causing trouble for the Tamers.

He also has an ego and is proud of being a free agent, mocking everyone else and trying to act superior. Although he's obviously a bad guy, his meanness is of a funny sort - he's not big and scary and trying to demolish large buildings. He does push his luck though, stretching the patience of Digimon stronger than him.