Pressing A Directional Button Away From Your Opponent And Pressing The Right Bumper Starts A Break Hold.
Taken From The Wiki
"A Break Hold is a special meter based action that allows the player to perform a special hold that can stop all strikes, from highs, mids, and even lows at the cost of 1/2 of their meter."
Most Do Roughly 1-5% of Max Health If The Hit Connects.
Its Not Very Damaging At All.
So If Youre Getting Punched In The Head A Lot -
Get Them To Low Health And Blast Them With <-- + Right Bumper!
Good Luck!