The Massacre Sword (originally Death Sword) is a recurring weapon in the Dragon Quest franchise. Despite being very powerful and able to strike every monster in all but one of it's appearances, it is a cursed item.
It can be used, however, without penalty, plus an addition companion in Chapter can equip it without the cursed effects.
The massacre sword has an attack bonus of +120. It can be found in Estark's Labyrinth.
The sword has been upgraded to hit all enemies now, and carries this trait in all subsequent games.
They are also sometimes dropped by Tormentaur.