Those who slay monsters must remain emotionless, excluding the feeling of relief when the deed is done. A slayer of monsters must remember that if the monster is allowed to live, the monster will bring about more death to those who are undeserving of such horror.
To feel sadness over the death of a monster is kind, but must not stay a slayer's hand. To revel in the death of a monster is to become a monster yourself, a piece at a time. In the end, when the trigger is pulled or the blade falls, the end goal of the violence must be a gift of peace; a peace that the monster could only achieve in its death. An end to the violence inherent in its existence.