At the expense of somebody/something

Pro Tip 1/2

Negative Connotation

This phrase often implies something negative happened as a result of prioritizing one thing over another.

He received a promotion at the expense of his colleagues' trust.

Pro Tip 2/2

Causal Relationship

Highlights the cause-and-effect aspect where one action directly results in harm or loss to another.

The company's rapid growth came at the expense of quality control.