noun
bane
BAYN/beɪn/
A cause of persistent trouble, misery, or ruin.
The invasive bindweed is the gardener's bane.

Etymology
Old English bana could name anything that caused death, not just a human killer. That deadly force broadened into something that causes ruin, misery, or persistent trouble.
In context
flips the letter over it was the one thing i needed most the trouble that had been looking for me it was the inevitability of all things the bane and purpose of my existence