ball-buster

[ bawl-buhs-ter ]
/ ˈbɔlˌbʌs tər /

noun Slang: Vulgar.

an arduous, often unpleasant task.
a person who makes great demands on others; taskmaster.
Also called ball-break·er [bawl-brey-ker] /ˈbɔlˌbreɪ kər/.