Somebody has been fined for reporting illegal parking to the city. Yes really, they say he has no legitimate interest in reporting people who park on the sidewalk in a way that's endangering pedestrians.

https://www-mucbook-de.translate.goog/wenn-datenschutz-falsc...

Go to https://www.enforcementtracker.com, which collects and publishes GDPR fine information. Type in "Private Individual" as a filter in the "Controller/Processor" column. I see twenty-ish results, mostly from Spain. My Spanish is rusty and non-technical, but I think some of those fines are about posting videos to social media.