[have] {sb} over a barrel

to place someone in a situation in which they have no choice but to accept one's offer or request

The origin of the idiom "have someone over a barrel" likely stems from literal scenarios involving physical restraint or vulnerability. It is related to the practice of punishing or disciplining individuals by placing them over a barrel, where they would be physically immobilized and unable to escape or resist. Another potential origin comes from the concept of barrel usage in the shipping industry. In the past, when a person was trapped inside a barrel, they would be at the mercy of those in control, as their movements would be severely restricted.

The unscrupulous landlord had the tenants over a barrel, raising the rent exorbitantly with no alternative affordable housing options available.
The company's monopoly in the industry put its competitors over a barrel, giving them no choice but to accept unfair business terms or risk going out of business.
The compromising photos gave the blackmailer the upper hand, holding their victim over a barrel and forcing them to comply with their demands.
The strict contract terms had the artist over a barrel, leaving them with no control over their own creative work and limited financial compensation.
The evidence of wrongdoing had the corrupt politician over a barrel, leaving them vulnerable to exposure and potential legal consequences.