Highest Risk - Lowest Probability
This is one of the least likely disasters to occur as it requires a nuclear war, revolution, civil war or other major event to bring it about. In preparing for a societal collapse a practical individual should first ensure that their preparations for more likely high risk disasters, such as hurricanes and earthquakes, are strong. Also while preparing for this event do not advertise that you believe this to be a coming about as such preparations may be misinterpreted as looking to start such an event.
Preparations for societal collapse will likely depend on complete self-sufficiency, protection from NBC attacks, and generous defense capabilities.
Adequate preparation for societal collapse is difficult as it usually requires the financial and familial support for removing oneself from most of society.