[quote=@Vocab]
[@Feisty-Pants] *Attempts to grab the antimatter and separate the Positrons from it, trying to render it useless*
[/quote]

That's the problem dear. She can conjure thousands of them all at once if she so chose. Then she could contain them, and you inside an telekinetic force field.

The second any of them touch a single atom of matter, their existing contradiction ceases to be in an extraordinarily powerful release of energy. Each explosion amongst thousands would not only be extrememly destructive, but the shockwaves themselves would bounce countless times off off the telekinetic field. Further increasing the damage dealt to the person insude, if they aren't simply disintegrated.

That way, Koto eliminates her target, and simultaneously limits the damage done to the city.

It's a win-win for her. IF she had to kill someone. Which she is actually highly against doing.