Hmm that's a tricky one. I guess there was one situation where one of the clients we built a website for turned out to be a scammer/con artist who got arrested for forex fraud. I guess our work in making their site look/function as well as possible sadly helped them gain customers to rip off, and gave them a false sense of legitimacy. But no one there knew the customer's company was a dodgy operation, so I guess hindsight is everything there.

I guess there have also been a few previous companies I worked on sites for that weren't exactly the most ethical operations overall.

But I don't think I can recall ever working on anything that was used for surveillance, or that itself was built for unethical ends. It's usually things associated with questionable companies that I didn't really know were questionable.