User blog comment:Trident81/The Most Powerful Quirk/@comment-24403746-20180626044348

https://bokunoheroacademia.wikia.com/wiki/Brainwashing

He basicly has to talk to an enemy once and just have them turn themselves in/tell their weaknesses or just let them kill themselves. People who don't know his quirk would've only realised after replying which at that point would already be to late.