We had dreadful neighbours in our last house, they used to get really pissed at the weekends and be generally obnoxious, tell lies to local council saying we had fly tipped etc, wrote racist language on their own garage and claimed that we did it (opposite neighbour had CCTV!) , when I was pregnant with DD the husband used to sing out the window if i walked past 'who ate all the pies etc etc' , they used to rip up our flowers in the front garden amongst many other crazy things.
It all came to a head one day when my DH was fixing his motorbike in our garage and neighbour came in and punched him, police called and neighbour arrested, went to court but no charges as his word against ours etc.
Neighbour wrote us a letter saying we were too noisy, young family - both working up at 6am, showers, new baby, shouldn't be using washing machine after 6pm etc, previous owner had been a single middle age man. Really unreasonable things and we were not noisy at all, in fact we went out of our way to be quieter so as not to start them off!
It certainly knocked my confidence, sanity and made me quite ill on reflection, nothing is worth that.
Saw the wife of the couple a few years back and she tried to engage me in conversation, totally blanked her and walked off.
Best thing we did moving, but it makes you wary, we don't really engage with our neighbours now, polite hello / quick chat but that's about it.