I can't say it was the worst by what I have read, but certainly the least favorable experience for me. It was 13 years ago as well so perhaps conditions have changed. I was in Jeddah Saudi Arabia on my way home from a Business Trip flying Saudi as it was part of the contract conditions that you had to fly them in and out of the Kingdom.
The Lounge was upstairs but the restrooms were downstairs and back then, a lot of the Haj Pilgrims traveled in the main terminal. I understand that there is a separate one for the Haj traffic now. Nevertheless, needed to use the facilities so off I went downstairs to join the gang.
Problem was that it was right before afternoon prayers and all of the "visitors" heading home from Mecca were washing up before prayer. Well, there I was, waiting to drain the lizard and all of the urinals were being used for wash basins. A little awkward doing my business just after someone washed their hands with a line behind me about to wash up as well.
Never so glad to leave somewhere as I was then.