Powerful Blow Question

[rob]

Is this option only available to the attacker, who passes his Kyu check, or can an opponent just declare they are making a powerful blow when defending?

I presume the former, since an action needs to be used before making a strike, but I've been wrong on some other assumptions as well, so thought I should ask.

[Rich Jones]

One of the few advantages of committing to the attack is being able to put some focus into it - thus only the 'attacker' as it needs an action