Vorpal Weapon

Until the spell ends, a weapon touch becomes indescribably sharp, ignoring resistance to slashing damage, and gains the Siege property, dealing double damage to inanimate objects such as structures. The weapon has a modifier of less than +3 to attack and damage rolls, its modifier becomes +3 to attack and damage rolls for the duration of the spell. Additionally, if a critical strike of this weapon would leave a creature with less than 50 hitpoints, the target creature is killed.

(From Artificer 1.7)