Karachi is one of the largest cities in the world, home to 17-million people, give or take a million. It is the economic engine of Pakistan, responsible for three-quarters of its economy. It is the bellwether for a precarious nation -- as Karachi goes, so goes Pakistan, they like to say here. It's also, according to a recent report from global human resources consulting firm Mercer, South Asia's lowest-ranking city for personal safety and the sixth most dangerous city in the world. It has had no elected government for more than 18 months, after the last one dissolved in bickering...