2 way tie between Casablanca and Dhaka.
Casablanca pax are so demanding. Last one I did was about 60% full in economy and the crew did not sit down the entire 8 hour flight including the 3 additional crew sent to help from business and first class because they were almost empty. We ran out of sugar tea and coffee with about 3 hours to go and almost had a riot on our hands.
Dhaka is all labourers that have never seen a western toilet let alone a plane before. They s%$t in the sink, on the floor and all four walls of every single toilet and this is usually before pushback. The smell in the cabin is unbearable and they pinch all the air fresheners so you can't even spray them.They pretty soon crack on to the fact that if you press the button on the control panel the pretty lady comes to your seat and leer at you when you get there. Their English consists of three words whisky beer and "fefsi" ( pepsi)
On the topic of war zones I have also flown to Khartoum and the passengers were angels.