I would encourage you to check the order of events, and look for where Lamech is described as "a mighty man" or "a man of renown".Your first mighty man described himself as infinitely vengeful l he is also the first polygamist.
Gen 4
And Lamech said unto his wives, Adah and Zillah, Hear my voice; ye wives of Lamech, hearken unto my speech: for I have slain a man to my wounding, and a young man to my hurt.
24 If Cain shall be avenged sevenfold, truly Lamech seventy and sevenfold.
Unless, of course, you trace the Hebrew terms through Scripture.There is no reason to think that there are anything but normal human beings in the story.