The worst check-in I have experienced has to have been at Kabul airport in 1987, when we were all standing around on the tarmac hoping a mujaheddin wouldn't take a pot shot at us from the hills.

Second worst would be any one of the zillion flights I took from DMO (Moscow Domodedovo) in the days before it was renovated. You can still see the old section of the terminal now from the new bit, and every time I look at it, I shudder from the memory...!

Anyone else?