The Sword Stab, also referred to as Sword Impale, is an Unblockable attack used by Yoshimitsu. The move is notable as Yoshimitsu uses his sword to stab straight through his opponent, inflicting heavy damage. He has had this attack since the original Tekken game. It is executed by pressing b,b+1 up until Tekken 6, where it is executed by pressing b,b+1+4 instead.
Yoshimitsu can also cancel out this attack and do the Sword Spin by pressing 1 right before the Sword Stab is pulled off, or the Ochimusha Hunter by pressing 1+2 right about using the buttons used to execute the Sword Stab.