Bane

Bane is a noun and means something that causes a lot of distress, unhappiness, or annoyance. These days it is usually used in a phrase that includes "of [appropriate possessive subject/prounoun] existence." For example the sentence "Dogs are the bane of Mary's existence" uses this construction. Often the word "bane" sounds archaic or old-fashioned used without the rest of the phrase. For instance, "Dogs are Mary's bane" certainly sounds old-fashioned at best and odd/incorrect at worst, but it is a perfectly fine sentence.

Interestingly bane is a very old word in English and comes from bana which means something that causes death or a poison. This can be heard in the Hallowe'en classic wolf'sbane. To this amateur etymologist, bana sounds like a name for a demon in Dungeon's and Dragons.