Actually, yes it is. It is a tool used to inflict harm and kill people, and Near even quoted it as a weapon. In this regard, it is without a doubt the deadliest weapon in anime history.
Black Sword that can break other swords. It also looks awesome. A US blacksmith company in Baltimore even made a video of forging a real world version of it.
If you don't like it Zabusa will slice you in half. Also if the sword is damaged, having it touch blood would repair it as ittakes the iron in the blood and use it to repair itself.