If we tried to describe false teachers, the word that fits best is evil. Jude wrote about their evil speaking, evil actions, evil natures, evil end, and evil influence.
The false teachers had given themselves over to evil thinking and behavior. They became their own authority and acted like irrational animals. Their evil behavior is associated with that of Cain, Balaam, and Korah. They thought only of themselves and were basically worthless in giving any genuine help to the people. In the end, they are going to face in judgment at the hand of the Lord Jesus Christ. They are fault finders and boast about themselves while taking advantage of others.