firebrand's heavy demon swoop, when fully charged, becomes unblockable
meaning that you can't block it, it actually breaks your block, same can be said for viper's fully charged focus attack
so a set-up is putting someone into a situation where they can't avoid it, a good example of this is using a lockdown assist with either of those 2 characters
so the set-up is simply, use a lockdown assist, hit opponent with unblockable, bnb, rinse and repeat
the only other unblockable set-ups are the high/lows, which means using the help of an assist, the assist hits either high or low while the point character does the opposite, a great example is using wesker's samurai edge assist, it hits low, so send out the assist and then jump in the air, if you time it right, the opponent cannot block this while he or she is on the ground (to avoid it, they simply have to chicken block)