Bane is a noun which chiefly means something which hurts or destroys. It is also a synonym for poison and death. Obsolete meanings include a murderer and a verb form which meant to murder by poisoning.
The word is most commonly heard in the phrase, or some version of the phrase, bane of my existence. The phrase is used to describing something or someone has the main cause of pain or woe in a person’s life. That phrase has been around since at least 1800.