Answer: stopatnothing

AnswerCrossword Clue
STOPATNOTHINGDo whatever it takes
STOPATNOTHINGAccept no limits...and the first of a quip
STOPATNOTHINGEnd of the quip
STOPATNOTHINGBe ruthless
STOPATNOTHINGCheap quip, Part 4