gang·bus·ter 
(găngbŭs′tər)
(găngbŭs′tər)n.
Slang
Slang
A law enforcement officer who works to break up organized criminal groups.
adj. also gangbusters
Idiom: Extremely successful: an experiment yielding gangbuster results; a profitable, gangbusters quarter.
like gangbusters Slang
With great impact, vigor, or zeal: came on like gangbusters at the start of his campaign; a career that took off like gangbusters.