[be] the death of {sb}

to cause extreme worry, distress, or discomfort for others

The origin of the idiom "be the death of someone" can be traced back to the 17th century. The phrase draws on the concept of something being so burdensome or aggravating that it metaphorically leads to a person's demise or extreme frustration. This expression can be used when discussing interpersonal conflicts, troublesome situations, or persistent irritations that have a detrimental effect on someone's well-being.

Her incessant nagging is the death of me; I can't take it anymore.
The constant noise from the construction next door is the death of our peaceful evenings.
That job was the death of him; the stress and long hours took a toll on his health.
His reckless driving habits were the death of their friendship; they couldn't trust him anymore.

to greatly upset, frustrate, or bring about harmful outcomes that can destroy or ruin a person or thing

The constant financial mismanagement proved to be the death of their business, leading to its ultimate closure.
Her toxic relationship became the death of her self-esteem and overall well-being, leaving her feeling broken and defeated.
The relentless cyberbullying he faced online was the death of his mental health, pushing him to the brink of despair.
The lack of proper maintenance and neglect proved to be the death of the historic building, resulting in its eventual decay and collapse.
The excessive workload and stress became the death of her work-life balance, causing burnout and deteriorating her overall quality of life.