Bake them cookies and bring them over.
When I first moved to my new house, I was dealing with the same sort of thing with my neighbors bordering our property. They were having loud parties, trashing my yard etc. I had my wife bake up some cookies and I bought them over with my (at the time) 4 year old. "Hello, we are your neighbors next door. We are new to the neighborhood. We just wanted to introduce ourselves". etc. Kill them with kindness.
Not one party since.
It should also be noted that the woman that greeted us when we brought over the cookies was all apologetic about the partying and everything, and I didn't even bring it up.
Tried and failed, and they just took advantage of our kindness.
We’ve been as kind and friendly with them as possible in all of our interactions. We’ve given them old clothes and toys for their kids; watched their kids before and let them play over at our house; on at least a dozen occasions helped them out at their request - jumping their car, giving them diapers, letting them use chargers and other lawn equipment, etc. And much more. And after all of the crap that they’ve put us through - hitting my car, waking us up in the middle of the night on weekdays in their drunken fights, having their fights spill into our yard and one time even into our house - they’ve never ONCE apologized to us.
I’m telling you, they’re just lowly, not good people. I try and give people the benefit of the doubt, but I also realize that some people truly just are lost abd not good people. After a year’s worth of putting up with this crap, it’s clear that they are in the latter camp.
And that makes it all the more difficult. They’re not reasonable people and don’t even realize how they’re affecting their neighbors, because they don’t know any better, meaning you simply can’t reason with them, as everyone who has tried has been threatened, which is why everyone just calls the police on a semi-daily basis anymore.