[Mailanka]

The problem with Kiai in combat is that it's a mental stun, and almost everyone will roll to recover at the end of their next turn (as most worthy opponents will have combat reflexes) which means you gave up an action to get them to give up an action, which is hardly worth it. Thus, Kiai is best for team actions (so someone can exploit the -4 penalty to defense from stunning) or, as it is an attack, you use it with Extra Attack, All-Out Attack, or you make a "rapid strike" with one of the attacks as Kiai. That means the Kiai comes up at the same time as the attack, so you can instantly exploit the penalty to defense.

Kiai came up often in CBR, unsurprisingly. I also made it the basis for a few chi powers. That said, it was definitely one of the less popular chi skills.