Remember, there is good and bad in every city. As there is in people.
So I don't have the WORST city because one person's WORST is the favorite of someone else. And you are Insulting the people who live in that city/town by saying "You live in the worst place in the world."
And I liked Sydney (the bridge and the opera house -- very special memories.) I enjoyed Melbourne better and found Cairns to be my favorite place in Australia.
As for culture, let people be. Except if they are bigoted or just plain stupid "like tourists in vegas saying 'Oooh, who needs to waste money to go to Europe -- the woman though Egypt was in Europe! when it's all here."
I simply shook my head at them as I got off the bus.
The absolute WORST place in the world is to be alone and without friends. Wherever you are.