Rundas
So he was able to deal with this much, not too shabby. The blows intensified in speed and power, but its not like she was holding back in the first place. Once she wielded her spear, she became death incarnate, and simply wasn't able to stop. Each and every blow was far from mindless, and a killing blow in itself. But she wanted to see how long the boy could hold on the defensive, so she didn't back down.
"Not bad, copycat! You've got nice intuition. C'mon, c'mon! Left, right, left, right!"
Her thrusts surpassed the might of cannonballs and reached speed rivaling military machine-guns. If he kept being pressured he'd be stepping backwards over and over until he lost his ground. In that case, even if he'd survive thanks to her power, it would be the sign that he could do nothing more than cower behind a stolen weapon like a craven, and she'd offer no mercy any longer.