I don't know if this qualifies as revenge, or just justice, but it's a good story, so I'll tell it.

For background - I live in the Phoenix area, so in the summer, air conditioning is not a luxury, it's a necessity.

Shady a/c tech put far too much freon in my system, charged me $500 for it, then every time the compressor turned on, it shook the house... The goal, I believe, was to ruin my old unit (a compressor will fail catastrophically if it pulls in liquid rather than gas) so they could sell me a new one for ~$8k. Overnight I went from knowing next to nothing about air conditioning to knowing enough to not take their shit... Gave the company the chance to make it right, but they doubled down, continued to say it was just because my system was old.

So I called another company - they found it was in fact massively overcharged, I had to pay ~$200 to have the excess freon removed (which, coincidentally was about what it should have cost to fix it properly in the first place).

Then I talked to my credit union to see if I could do a chargeback- I had used my debit card to pay the shady company. At first they were reluctant to take it on, since it wasn't the typical fraud case, they said it would be very difficult to prove- but because I had done the research and had everything laid out for them, they started the process. There was some back and forth, my offense was all technical with sources cited, the company's defense amounted to "we have x satisfied customers and have been in business for y years"... at one point the owner of the company called me, talked shit about me spending "a few minutes on the internet" and thinking I was an expert, and threatened to take me to court- I said "go ahead, then this will all be public record." He didn't sue me. I won the chargeback and never heard from the company or the owner again.