F**k, it doesnt work from scripts at least. I wrote something like this in LAi_ApplyCharacterAttackDamage:
if(stunEnable)
{
enemy.actions.hit_attack.h1 = "";
enemy.actions.hit_attack.h2 = "";
enemy.actions.hit_attack.h3 = "";
}
But actually enemy has this animations. I think it will work only after reLogin. And now I absolutly know, that it should work in engine. If I (or u) could create event, which will calculate chance of "NonStun" it gonna be great addition to fighting. I know how to write events code, but i cant change engine for this event, which should let Char to stun after hit, or doesnt let, in dependence of events calculations results.