Conservation of Ninjutsu. It was what doomed her sisters when they fought Jack.

This series has shown before that you need quality over quantity. Many a time an entire army will be nothing but jobbers.

The beetle-drones from the start of the series, the robots that the three archers take out, that one army that Jack beats by doing absolutely nothing… The only army that ever really came close were those celtic-demons, but the Scotsman's wife handled them pretty easily.

Frankly, Ashi and the Scostman's wife might be the biggest badasses. They kick ass with nothing but their bare hands.