could destroy school building

A sudden explosive tremor hit them—and not only the school building, or only the
gymnasium, or only the schoolyard. Every object on the entire school grounds creaked,
squealed, and bounced around.

There was a pool behind the school building, though it wasn’t visible from here because
it was on the other side. That’s where the explosion originated.
And despite an entire building standing between them, a thin spray of water hit
Kongou’s flushed cheeks, immediately giving her cause to shudder. Something had
made that blast of pool water fly all the way out here, after all.

“...Wh...What in the world was that?” Kongou, surprised, the droplets of water striking
her face, was shivering as though she’d just been licked. Then she put her hand to her
cheek, stared up at the sky, then back down to the school building.
“Oh, that’s right. You only transferred in for the second semester, so you don’t know.
That was the Ace of Tokiwadai.”
That made Kongou remember.

There could only be one girl standing there at the pool behind the school building.
A girl who, despite being a ranged attack user like Shirai and Kongou, was an esper so
tremendously strong that it put the teachers at Tokiwadai to shame for being unable to
measure her enormous destructive power with their usual instruments.
The school had assigned her a curriculum particular to her needs. Even all the water
stored in the entire pool wasn’t enough to dull her power—she could destroy the entire
school building along with all the measuring equipment. A Level 5, of which only two
existed in all of Tokiwadai Middle School.

Misaka Mikoto—the Railgun.

- Toaru Majutsu no Index Volume 8, Prologue