I wonder what the course of action would be for someone who is so petrified of their abusive neighbour that they are too scared to speak up?

The family in question have young children (not the abusive ones I do not mean) and are too scared to speak out against their neighbours who have threatened to smash all of their faces in.
The lovely people in question have already been moved from one council estate as they were violent and aggressive towards their neighbours so we were thrown out, now my friend has the pleasure of living next to them.

He, is built like a ten tonne truck and you sure would not confront the bloke.
What would be your advice Nick?
How would someone be protected in a case such as this?