I’m talking about things you decided to do on purpose, and then deeply regretted later.
Me personally, my biggest database regret was that time almost twenty years ago when I ran a Profiler trace from my desktop computer.
My very slow desktop computer.
Which was connected to production over a VPN.
I can’t remember what happened first – running out of space on my C drive, or my VPN disconnecting – but in the hot mess of it all, I fielded a call from my manager asking about why the production SQL Server kept freezing up. Everything about that situation was frustrating.