Punchbag is an aggressive compressor designed to create massive punch into percussive and bass. Not recommended on continuous programme.
It offers the response of an aggressive punch-delay compressor. An RMS compressor on steroids. The attack phase is delayed with onset-delay and then a fast attack time to create ultimate punch. The recovery release is also fast. This creates punch and fast ballistics. The side-effect is intermodulation distortion, which can sound good or bad depending on programme.
As with any other compressor, the best advice is to try it on different sources and see if it suits your mix.