Synonyms for Taskmaster:

n.

disciplinarian, autocrat, dictator, big brother, gatekeeper, tyrant, nag, control freak, martinet. head, foreperson, over, forewoman, taskmistress, straw boss. director (noun)
foreman, mayor, director, commandant, queen, executive, ringleader, officer, general, overseer, superintendent, conductor, magistrate, band master, chief, captain, administrator, warden, master, lord, boss, commander, overlord, ringmaster, supervisor, baron, ruler, governor, leader, dean, manager, king.
forewoman (noun)
foreperson.
martinet (noun)
martinet.
master (noun)
commandant, ruler.
over (noun)
inspector, monitor.
slave driver (noun)
foreperson, supervisor, manager, tyrant, overseer, boss, disciplinarian, director.

Other synonyms:

forewoman, taskmistress, martinet, control freak, straw boss, big brother, foreperson, dictator. gatekeeper, autocrat, tyrant. nag. head. trainer
disciplinarian.
Other relevant words:
forewoman, disciplinarian, tyrant, autocrat, head, straw boss, monitor, inspector, dictator, martinet, taskmistress, foreperson.

Usage examples for taskmaster

  1. Our liveliest sympathies attend these white brethren- torn from their homes, the ties of family and friendship rudely severed, parent separated from child and husband from wife, exposed at public sale like cattle, and dependent, like cattle, upon the uncertain will of an arbitrary taskmaster – White Slavery in the Barbary States by Charles Sumner
  2. A better proof of the severity of my bondage to that taskmaster could scarcely be afforded, than the degrading shifts to which I was constantly driven to find him employment. – Great Expectations by Charles Dickens