At my last company thankfully I was able to limit the losses to just under $450k which sounds like a lot, and it is, but it could have been about $5m/yr. I didn't sabotage anything, either. It was mostly through simply asking a lot of questions early, repeatedly suggesting we write plans down and make sure everyone on the project is up to day, and suggesting we test drive components before buying the whole car.
Spent a bunch of money, rolled out the pilot project to 70 folks, and began 30 day checkins. After 30 days we had a retention rate over 80%. By the 60 day mark, we were down to 40%. By day 90 we were at 22% and landed at 11% after 4 months and never went higher. By month 8 we cancelled the project and the 8 people still using the tool were ok letting it go, feeling it didn't help that much.
All because someone from the board said, "we need to use AI, anyone not using AI in a year will be out of business." The CEO asked what we should use it for, and the board member said, "I have no idea, that's your job. But we need AI somewhere. Look here, it can buy a plane ticket for me now!" and then wasted the next 40 minutes of the meeting talking about how amazing AI agents were. We're not a tech company, he was definitely NOT a tech person.