underbelly

1. (figuratively) The side which is not normally seen, normally a dark, immoral place.Examples: "The area by the canal is the underbelly of town – not something you’d see in the guidebooks."; "In order to take the initiative, military leaders from Great Britain and the United States decided to attack in Africa, cross the Mediterranean, and move up against the "soft underbelly" of German-dominated Europe."; "The documents in this report reveal how such doctrinal disagreements have historically driven wedges within the upper echelons of al-Qa'ida. It is this intra-movement contention that comprises the soft underbelly of violent jihad, which can be exploited to great ends."figuratively