What did it take to be a legend?
Prior to WW2, there were Immortal Level Overlords all over the globe in both the eastern and the western world, leaving many colorful tales about their legendary lives. They could easily bring a nation to heel, playing the kings and monarchs with ease. They were behind many turning points of history and played a significant role in all the significant events.
However, ever since American dropped two atomic bombs on Japan, ushering in the nuclear age, even the strongest overlord had to keep his tail between his legs. The power dynamic shifted and gave the nations of the world more advantage against powerful individuals.