My upstairs neighbours in my apartment building were AWFUL. For one, their air conditioner flooded their balcony and slowly but constantly dribbled onto ours all summer, causing water damage to the wooden ledge. There’s still a green rotten spot there. Second, they always insisted on watching movies and listening to music at eardrum-piercing volumes at all times, day and night. It was so loud that I could tell what movies they were watching and what album they were listening to - from both inside my apartment and all down the common hallway on the level BELOW them. So one afternoon, after they’d watched Drive (great movie but COME ON I was trying to nap) My girlfriend and I went and knocked on their door to give them a piece of our sleep-deprived minds, and we were greeted by the sound of them locking their door and walking away. So I wrote them a desperate letter instead. It didn’t do much.
Luckily they moved out a few months later (but only after throwing a Thursday night rager where someone puked off the balcony and woke up my roommate during finals week).