-Analysis- BUENOS AIRES — It may be too much to use the “bloodbath” as some have to describe what criminals have wrought in Rosario, the riverside district northwest of the Argentine capital. But in one sector there, the size of one-fifth of the city, the rate of criminal killings has become comparable to those of Medellín in the 1980s, the worst years of the Colombian city’s drug cartel violence. These are cold and hard numbers, not hyperbole. Figures show Rosario has a crime rate that is four or five times the average rate of Argentina’s main cities. For the latest news & views from every co…