at the expense of

causing a negative consequence or cost to someone or something in order to benefit another

His success came at the expense of his personal life, as he devoted all his time to work.
She pursued her career goals relentlessly, often at the expense of her personal relationships.
The company prioritized profit margins at the expense of employee satisfaction.
His success came at the expense of his health, as he sacrificed sleep and exercise to meet deadlines.
The politician's popularity rose, but it came at the expense of his integrity.