An unusual problem

Dynamat products are used to dampen the inside of car doors to quiet the inside of your car, improving the sound of car audio.  This may work well to dampen the glass vibrations.  

There are also quilted blankets, woven with batting available, much like the packing blankets Penske trucks issues.  These can be found with metal grommets so one can suspend them on the wall with small nails.  They can weigh 9lbs. each.

Unfortunately your problem isn’t that unusual, it’s just one of the pitfalls of sharing a common wall with your neighbor. You can try some mitigation, but realistically you’re just going to have to turn everything down in the late hours.

but realistically you’re just going to have to turn everything down in the late hours.

Not just late hours but all the time except when theyre not in. 

Buy an Auralex Sub Dude isolation platform.  I've had one for years ...not only does it improve the sound but it eliminates many rattles associated with having a sub.  My mom had been complaining that my dad's sub was boomy and keeping her up....  he's 76 so sometimes movies are a little louder than they should be.  He says "does anybody ever say turn it down at the theater?"   Touche, I guess.  Anyway  I went over there one Saturday when he wasn't home and slipped a sub dude under the sub and ran the Anthem room correction software again and it's never sounded better.  Boominess is gone and you don't feel it in other rooms now unless it's loud.  One of the greatest accessories ever.

I have a Subdude in my bedroom.  I live in a house, but my neighbor's house is not too far away.  I think it helps a little, I never went outside with my SPL meter to see if it made a difference or not.  Eventually I just quit using the sub in there.  They never complained, but I was trying to be proactive.

There's this thing called consideration that you can get for free.  If you live in a box right next to someone in another box, don't play your music loud after 10 PM.  Headphones are a good suggestion.  That's what I do late at night.