To answer your question, gather as much written evidence as you can from your neighbours and get an AVO that forces this person to leave you alone. This is not a strata issue – it’s a neighbourhood issue and has nothing to do with your strata plan.
There are bullies outside of strata too, Me, I’m fed up with people who have issues with neighbours and blame it on living in strata.
One good thing about strata is that you are not alone – and I could tell you plenty of stories about nasty and aggressive neighbours in standalone houses who have made the lives of the people living next to them a misery … and they haven’t had anyone to support them.