When in Hollywood movies the bad guy asks the action hero's name, the cult answer is: "Your worst nightmare." As from today, German food retailers will at least find out whether Amazon Fresh is a game changer.They have certainly long been in denial. In a relentless hunt for sales, without even a cursory glance at the return on invested capital, local bricks & mortar retailers still can't build enough physical stores. This inexorable process has continued, regardless of how late such stores may be in their life cycle; regardless of the fact that Germany is already overstored by at least a third; and regardless of the growing consumer trend towards internet shopping.For years would-be pundits have comforted themselves by saying that the German market is so dominated by hard discounters that no online food retailer could ever make a profit here. For those readers who are not quite so sure, it might be worth looking at what Amazon has just begun in parts of Berlin and Potsdam.