Barbus

Barbus is the Demon of Fear, an ancient, powerful Upper Level Demon who had lived for thousands of years. His key ability to read a person's greatest fear, and then turn it against them, either literally scaring his victims to death with illusions, or manipulating them into doing what he wants.

Originally, he was "bonded" to the Underworld, and could only appear on earth once every thirteen centuries, on Friday the 13th, for twenty-four hours. However, if he could kill thirteen unmarried witches before midnight, then he would be able to break free of his bonds and walk the earth for eternity. This later changed, as he started appearing more frequently, his first vanquish to purgatory likely having broken the cycle.

To defeat Barbus, overcoming your greatest fear is essential. The Charmed Ones managed to vanquish him four times throughout the course of the series, all by overcoming their greatest fears and using spells/potions, though he later found a way to come back and escape from purgatory each of the first three times. The last time we see him being vanquished came with assistance of the Avatars manipulations, as well as the sisters and Leo hunting him down for helping Gideon target Wyatt.