An unblockable attack is just how it sounds, it's an attack that cannot be blocked, although they can be possibly avoided by either Jumping. Side Steping or by interupting their power up. These moves sometimes takes away a good chunk of the opponent's health. These type of unblockable attacks are pulled off slowly for this reason, making it easier to dodge.
In some cases, an unblockable move is a projectile, including Devil/Angel and Devil Jin's laser attacks, True Ogre and Gon's firebreath attacks, Jinpachi Mishima's fireball and Alisa Bosconovitch's rocket punch.
In addition to unblockable attacks, every character has a throw move, which can't be blocked either, but can be countered.
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