Vast and powerful vertically and/or horizontally integrated corporations developed in Japan (the zaibatsu, later keiretsu) and South Korea (the chaebol). At times only a handful of these companies, corporations, or conglomerates owned and controlled the majority of each nations economy. They have lost some power since their peak in the 80s or 90s, but still hold enormous sway. Samsung, Sony, Mitsubishi are examples.
Could one corporation have possibly gained even more power, to the point of over half the Korean or Japanese economies being under the control of a single board of directors? Are there other countries where this might be more likely? What would be the effects of a single organization having monopolies on transportation, banking, insurance, electricity, communications, and the majority of industrial goods?