Psychopath
A psychopath is a person who tries to harm others.

Much of the psychopath's work will be non-physical. It will include bullying. Bullies are essentially psychopaths.

A psychopath has no morality. They will try to get people to worry, and the more they traumatise people, the happier the psychopath is.

They will often try to turn people against each-other, and will always pick a person and make an attempt to destroy their life.

Psychopaths stand up for psychopaths, and will attack in groups.
I'd like to know why that psychopath is trying to ostracise me from the group.

Sean, the psychopath, kept kicking, punching, and throwing sharp metal objects at me.