Aizawa weaponizes class 1-As personality quirks.

It started when he saw Mina messing around seeing if Iida can chop through wood when hand chopping. He can. Aizawa sees this and, in a moment of brilliance that would make Nezu envious, decides to teach his students how to weaponize their personality quirks.

He explains to Izuku his muttering is creepy because people can't hear what he's saying. But if he spoke clearly people would be terrified. This leads to Deku destroying most of Overhauls gang by tearing their quirks apart and making them question everything they know about themselves.