A bane is a curse, or the cause of distress, death, or ruin. In Leo Tolstoy's War and Peace, Anna Pavlovna talks with Prince Vassily Kuragin, telling him how charming his three children are. The prince, however, has a different opinion:
I am your faithful slave and to you alone I can confess that my children are the bane of my life. It is the cross I have to bear. That is how I explain it to myself. It can't be helped!