True block strings allow players to maintain pressure through well-timed button presses mixed in with special moves, but if there are gaps in the timing, or if certain attacks just don’t quite fit together perfectly, punish options begin to present themselves. These windows are small and defenders need to know to expect them in order to be able to perform a proper punish as opposed to just waiting until the block string is over.
Dudley’s duck, as you’ll see in the video below, allows for a great number of these situations to turn into huge damage in Ultra Street Fighter IV. Many of the punish options–mostly those involving canceling a normal into a fireball–don’t come as a huge surprise, but then there are things like meeting Yun’s EX lunge punch with Dudley’s EX duck, which may not have been so readily apparent even to veterans of the character.
Of course, since this is a video from Forbidden Technique, they’ve not only included what version of ducking will net punishes in an alarming amount of scenarios, but have also offered up optimal combos to tack on and keep opponents scared to apply pressure.
Source: Forbidden Technique TV