I did 2 things to one neighbour.

When I was younger, we had a neighbour who was a keen gardener, his lawn was well maintained and his flower beds and hedges kept in perfect condition.

He was also very nasty to all the kids who would play out in the street quite often screaming at them to play outside their own homes.

When his car wasn't in his garage he parked his car outside his home on the road in what he claimed was his personal space, yelling at people to move their car if he wanted to park there.

One day I had nowhere to park outside my home so parked outside the neighbours house, less than a minute later he was out telling me to move it, threatening me and threatening to damage my car, he also told me I didn't amount to much in life. I just laughed at him, called his bluff which infuriated him more, I walked off and he stormed back in his house.

I can be quite laid back but while rattled will hold a grudge so this wasn't the end of it. A few days later I was shopping, I was looking at weed killers when I spotted cress seed packets, a dozen packs later and I was off.

Middle of the night I went back to my neighbours house and sprinkled the seed packs everywhere and waited. The seeds took and my neighbours perfect lawn was ruined, even if he cut the grass the cress grew back, he had no choice but to have the lawn removed.

The less sneaky part of my revenge, the neighbour rented his house from the local council, I made a complaint to the housing officer about his threatening behaviour towards me, as it was a clear breach of his tenancy they had no choice but to issue him a warning notice which included reminding him parking on a public highway wasn't allocated to any household and was first come first serve.