Sentence:  America's poverty line is $63 a day for a family of four. In the richer parts of the emerging world $4 a day is the poverty barrier. But poverty's <WSD>scourge</WSD> is fiercest below $1.25 ([...]): people below that level live lives that are poor, nasty, brutish and short. 
Meaning of the word marked with <WSD> tags:  A means to inflict such pain or destruction.