End of All (E.o.A.) Smite

The next time you hit with a melee weapon attack, you may use your bonus action to cast this spell, your attack deals necrotic damage equal to your current hitpoints.  Additionally, you suffer that same amount of damage, bringing your hitpoints to 0 and rendering you unconscious.  If the creatures hitpoints are also brought to 0 during this attack they must succeed a Constitution saving throw against your spell save DC or be killed instantly.  The creature can not be revived by any means including the wish spell.  Their soul, body and mind are extinguished from existence.