Probably the
Catapult attack is the most unstoppable of all attacks, because even when exists
Units
serving as
Cannon Fodder, they are useless in this case.
The
Catapult ignore any unit that is in its front, friend or foe unit, and it is enable to attack
any enemy unit that is in its
Range. An example is the following image:

This attack is perfect for surgical strikes behind a defensive barrier.
Another feature that makes this attack very interesting, is the
Strike Back of the attacked unit be ignored
if the unit that shoots have a unit between it and attacked unit.