1) Animated series villain 2) Any Simon Legree 3) Bully boss 4) Burdensome boss 5) Fictional assassin 6) Fictional secret agent 7) Imposer of hard work 8) One who enforces hard work 9) Overseer, usually hard 10) Simon legree 11) Slave driver 12) Stern boss 13) Supervisor 1) Boss 2) Slave driver 3) Taskmistress 4) Tyrant 
• (n.) One who imposes a task, or burdens another with labor; one whose duty is to assign tasks; an overseer.
Task'mas`ter noun One who imposes a task, or burdens another with labor; one whose duty is to assign tasks; an overseer. Ex. i. 11. « All is, if I have grace to use it so, As ever in my great Taskmaster's eye.» Milton. 
[n] - someone who imposes hard or continuous work
noun someone who imposes hard or continuous work