I was recently reminded of a very effective workplace exposure story:

Married man is having an affair.
OW doesn't know the man was married. (irrelevant though)
BW learns about the affair.
BW investigates where the OW lives and works.
BW gathers up cheating husband's dirty clothes in a bag, dirty underwear and socks included.
BW drives to OW's workplace, asks to speak to OW.
When OW meets BW in lobby, BW loudly says something along the lines of ...

"I understand that you're having an affair with my husband. We have a good marriage, but it's certainly not perfect. How can it be when we're busy raising four young kids? I'm asking you woman to woman to stay away from their father. But if you continue to have sex with him, then I just want to let you know that you can start doing his laundry too."

And then the BW dumps the pile of laundry on the floor and walks out of the building.

Co-workers and customers hear the full exchange.

How powerful would it be for management and HR to receive a very matter of fact letter the same day from BW about the affair?

There are so many potential deviations to this: exposing in similar fashion at a PTA meeting, church, country club, restaurant.

And of course if dirty clothing wasn't available, I'm thinking a stack of bills would be a good substitute.

HA !

You jest.

Well, my girlfriend didn't do this in a public place, but after her WH had been shacked up with the OW for a week, he brought his dirty clothes home and dumped them in the laundry room floor for his BW to wash. He then left.

His BW was already planning to file for divorce, so she loaded up the clothes, took them to OW's house, knocked on her door and said, "Since you're s****ing my husband, you can wash his d*** clothes, too!" She then dumped the clothes on the front steps and went back home.