slave-driver

noun3

1. •
   An overseer of slaves at work; a person who puts slaves to work.

   • "That's the rifle I used against the Peruvian slave-drivers three years ago." — 1912
2. •
   (informal, figurative) An employer or supervisor who demands excessive amounts of work from an employee.

   • He's such a slave-driver! I can't believe he wants us to come in on Saturday.
3. •
   (informal, figurative) Anyone who requests an amount of work from others that is deemed unreasonable.

   • Mom, I need a break after doing homework! You're nothing but a slave-driver!