Is there an eye-witness account of him? To me, the Quran is the Word of God, and God was there when Abraham entered into argument with a king.
Have you not turned your vision to one who disputed with Abraham about his Lord, because Allah had granted him power?” Says God in Chapter 2, Verse 258. Abraham said, ‘My Lord is He Who gives life and death.’ He said, ‘I give life and death.’ Abraham said, ‘But Allah causes the sun to rise from the east. Do thou then cause it to rise from the West!’ Thus was he confounded who rejected faith – Allah does not give guidance to a people unjust.
Next: the literature of Nimrod (“the king” who opposed Abraham)