She had merely made a motion similar to flicking a small piece of filth with her finger, but it produced a strike that was even more dreadful than a shell from a battleship. It flew by right next to Hamazura and struck a drum. The fuel within the drum ignited and the blast sent him 5 meters through the air.

If she had wanted to, she surely would have been able to kill him instantly.

The only reason she hadn’t was because she wanted to torment him more before killing him.

Toaru Majutsu no Index vol.19 ch.4 pt.2