Some years ago I replaced my turf lawn with shrubs and native plants and he hated it. He got all pissy and demanded to know why, saying, "I like grass!" and I replied that I didn't like grass, and I was tired of mowing the slope down to the sidewalk, and it was my lawn anyhow. For years there were repeated little incursions. He complained that my shrubs made it impossible for him to put up a ladder to change his second-floor storm windows, although there really was plenty of room, so he put his ladder on my shrubs and squashed them. He threw his yard waste in the Dumpster I'd hired when I was doing some remodeling, which was plainly labeled NO YARD WASTE, so I had to climb into it and haul out the tree branches.
One day he and his shrewish wife came to my door and demanded that I cut down the trees in my back yard because they were overhanging his yard and would interfere with their electrical lines from the utility pole. I told him I was not going to cut down my trees but that he was legally allowed to trim overhanging branches. He told me I would have to pay for that work, which I refused. Nothing happened after that for many months, until one day I came home to find that he'd had someone saw large branches off my trees well into my side of the property line, and they'd thrown the branches onto my yard. After that I had a 6' fence put up between my yard and theirs.
The following summer they were doing some more tree trimming, and, obscured by my fence, I heard the shrew tell the workers to just throw the branches over the fence, but the workers told her they couldn't do that. The last straw was when I discovered that all the plants and shrubs on a 18" strip along the property line on my side had been poisoned, apparently with something like Round-Up, and everything on the strip was dead or dying. At this point I got a lawyer involved, and now they were claiming that the property line wasn't where it had obviously been for decades, and they'd never claimed otherwise before even though their own landscaping extended only to the existing property line. And I pointed out where the 100-year-old survey markers were and told them they could get the property surveyed themselves if they wanted, so that was the end of that. I never did get any relief on the plant-poisoning, though I did notify the police so I could make an insurance claim for vandalism. I didn't have proof they did it, though nobody else had either the motive or the opportunity, and it wasn't worth the effort to go to small claims court over it.
They moved away three years ago, probably to a development where there is a fascist homeowners' association of which he or she is now probably the chair, and they amuse themselves by pestering residents about the color of their mailboxes and maybe someone is growing tomatoes in their front yard where the hydrangeas should be. So that's my shitty neighbor story.