I think if powdered it would be one of those aromatics which quickly loses it's punch. I'm surprised you don't find whole Star Anise strong enough. I use 1 whole star in the preperation of a Jalfrazi and it comes through perfectly balanced and is a key contributor to getting the correct Jalfrazi flavour profile (at least the ones I'm familiar with). And like the others mention, it's key in Pillau rice. I'd suggest sticking with whole and just add more if you can't get the flavour through.