with the Surprise Blow. The Surprise Blow is an not an unblockable move, but it stuns the opponent afterwards if it is not blocked. Every character has a unique Surprise Blow, which is performed by pressing MP + MK together. Also unlike the Guard Break, the Surprise Blow does not require a Super Combo level. A Surprise Blow can also be used as a Momentary Combo (see below).
(The Surprise Blow was called a Hard Attack in the Japanese version of the game. More typical useless Capcom name changes to protect us dirty-minded Americans.)