Ironically, my worst is also my best neighbor.
The lady who actually lives there is pretty nice - a bit peppery, but nice. We look after each other's animals when out of town. We visit and chat. I've helped her during surgery, she is helping me during my upcoming surgery. She's quiet (aside from a barky dog - a problem we were able to solve constructively together). Her family is another matter.
Her son has mental issues - one of them does, anyway. As part of those, he tends to think that he owns parts of the neighborhood he can see from his mother's yard. He was overheard threatening to tear down our brand-new shed because we'd built it without his permission. His father was attempting to settle him down, and nothing ever came of it (2 years ago). However, that event came in the wake of another that was even more stressful.
A few months earlier, we were in the process of scraping a large amount of pea gravel from our yard. Pea gravel, you may know, is heavy. It is attractive, but we had other plans, so we hired another neighbor to help scrape it up. Trying to come up with a way to dispose of it, we offered it to our nice neighbor, for an unattractive weed-patch of an area that's been untouched the entire time we lived here. A trailer sits on that patch, rotting, and the old white gravel is thin enough to admit a ton of weeds to grow through. She gladly accepted a fresh covering of gravel. Accordingly, the neighbor we hired and my husband spent the best part of a day shoveling it into wheelbarrows and hauling it over to her yard.
The next day, her husband saw the gravel and went ballistic. He was screaming and threatening to hit both my husband and the other neighbor with a shovel. Actually threw a shovel at the other neighbor - across the street. It missed, of course, but he was livid. He insisted that this weed-covered, bare patch was a critical, carefully engineered drainage pathway, and that they used that space ALL THE TIME. The gravel would ruin the drainage and ruin the space. His wife was "just a woman" and so was too stupid to know how to manage her own property (he has actually no ownership interest in the house whatsoever - but he comes to help with the yardwork all the time). To keep the peace, it was necessary to move the gravel again. Fortunately, the neighbor who'd helped move it was willing to put it on his property, which they'd made over not long ago in pretty much the same pea gravel. Another neighbor decided it would be the very thing for an area in his yard he hadn't decided how to handle.
The angry ex was threatened with restraining orders, and his ex-wife ordered him to apologize. He never did apologize to my husband, which is just as well. I am the only one who will go over there when he is around, because sometimes, somebody's got to for one reason or another.
tl/dr: Nice neighbor lady has a slightly crazy family that has threatened property damage and even serious bodily injury, over things like making improvements to our property, and a gift of pea gravel.