Nah, there's nothing louder than silence.

Wipe all expression from your face, and stare at them. Maybe just an expression of incredulity if this is out of character for them. That's all it takes.

Bystanders will literally stop what they're doing and watch. Their brains will scream "I'm about to be excluded from the group", and they'll start babbling. They'll confess their sins and be harsher on themselves than anything you could say

If you don't like their next words, give them nothing. Literally don't respond, anything you give them is closure. Don't give them closure, move on with your life - they can't.

Don't give them judgement, give them nothing. If you judge them, they can turn themselves into a victim or you into an enemy... Without a response, the only enemy is themselves, because they will crave your approval.

It's like a teacher staring down a student who keeps talking until the whole class is looking at them, except they don't know what to do to make it stop. So they try anything and wrack their brain for a solution. It seriously freaks people out

Note: this is less likely to work against neurodivergent people, they'll just be confused. That's how I learned to do this - I got annoyed and straight up asked a therapist why they kept staring at me when I was done talking. They explained the concept of a pregnant pause, and so I started using it.

And acquaintances started telling me how they were abused to explain their behavior and strangers started confessing how they cheated on their partners out of nowhere.

I get a lot of long apology emails the day after someone wrongs me, I now make an effort to give closure to everyone I like early and often.

Humans are tortured by this