break a butterfly on a wheel use unnecessary force in destroying something fragile or insignificant.
☞ In former times, breaking someone upon the wheel was a form of punishment or torture which involved fastening criminals to a wheel so that their bones would be broken or dislocated.
2002Times There were plenty of implausibilities in Ella and the Mothers, if you stopped and thought about it too much, but that would be to break a butterfly upon a wheel.