Yeah, that was certainly my favorite of the fox tricks as well. To be honest, it tricked even me.

Tensaiga's new power must be quite formidable indeed as it seems more metaphysical than physical. Though I suppose that depends on whether he must manage to physically cut whatever he intends to send to the next world. If that's the case, then it might "only" be a sure way to kill, not a way to bypass physical limitations.