slave-drivers

A slave-driver was historically an overseer who supervised and often brutalized enslaved workers, forcing them to labor under threat of violence.

The term now functions almost entirely as a figurative complaint about any demanding boss, teacher, or authority figure who pushes people relentlessly: My new manager is a real slave-driver—she expects us to work weekends.

The hyperbolic comparison trivializes the historical reality while conveying that someone feels overworked or harshly supervised.