I got a new neighbour across the hallway about a year ago. First met him as he was emptying my storage room to put his own stuff in there. He yelled at me when I asked him what he was doing.
Since then, he's been insistently greeting me.
Just now, I came across him in the washroom and again he greeted me. When I didn't reply, he slammed the drier door shut and began yelling at me.
I told him "fuck you" and he yelled even more. Then I complained to the landlord again.