The Executioner's Mercy

Requires attunement by a good aligned Paladin or Cleric.
+1 to attack and damage rolls against evil aligned creatures.
When you attack a creature willing to die from this weapon, you cut off one of its heads.
The creature dies if it can't survive without the lost
head. If a Evil or Neutral creature dies this way its allingment shifts to Good.
When you score a critical hit on a Evil creature, the damage from the sword is maximized.