Cush fathered Nimrod; he was the first on earth to be a mighty man.
Genesis 10:8

This seems to contradict Genesis 6:4, which says that the Nephilim who lived before and after the Great Flood "were the mighty men of old". The two verses can be reconciled by understanding that the "mighty men" reputation of the Nephilim was applied posthumously in the myths that grew up around them, legends of giants, demi-gods, and the like.