Vanquishing

Vanquishing is the term that describes the destruction of a magical being, namely the forces of evil such as demons and warlocks. The death of a mortal or a force of good such as witches is usually called killing instead.

In the process of vanquishing, beings are often destroyed in a (sometimes very) violent manner such as bursting into flame, exploding or even being obliterated. Most vanquishes will never leave any trace of remains behind and do not damage the surroundings or objects near the destroyed being. This is so any existence of magic is hidden from the mortal world. However, big explosions can cause windows to shatter and energy balls are known to leave a scorch mark behind (some beings can even be identified by these scorch marks, such as Belthazor).

Ways to Vanquish
Vanquishing can be achieved in many ways; Some evil beings require a specific spell or potion, sometimes needing to be blessed by the Power of Three, or a piece of their own flesh (required to vanquish Upper-Level demons). A weapon can be pretty much anything from a knife to a high heel.
 * with spells and potions
 * with powers
 * with weapons, both magical and normal weapons

Banishing
Sort of like vanquishing, banishing is the act of casting a being out a certain location or to another plane, making it so they can never return. This can only be achieved through spells and potions.

Beings that can't be vanquished like Barbas, the Demon of Fear, can only be banished back to the Underworld or more likely Purgatory. These beings can then make pacts or agreements with other demons to break free from their banishment.

Notes and Trivia

 * Once vanquished, evil beings are send to the Demonic Wasteland, where their body and powers are separated upon arrival, the body being destroyed in flames and their powers absorbed by a monstrous thing called the Beast.
 * Even though a being had been completely destroyed, some demons can perform dark rituals and resurrect the once vanquished demon.
 * Soul Killing is the method to destroy another being's soul or essence.