Okay I didnt feel like reading all the posts, so if any of these have already been mentioned, sorry.
Assuming he existed King David. He went from musician to king, killed a giant with a stone, and created an empire at a time when technologically superior and more populous people occupied the area (Philistines, Egyptions, Sea Peoples(?)) Also the fact that he consolidated and further unified a fractured people. Plus his son was Solomon. And Solomon is easily the most bad assed, if entirely exagerated Jew ever.
My second nomination goes to King Leonidas, who certainly existed and decided to spit in the face of the most powerful empire to ever exist up until that time. He also did it with only 300 spartans. And under his leadership a force of about 7000 spear armed greek farmers (everyone was a farmer in those days, except for athens and sparta, and no athenians were at the land battle of thermopylae) defeated, humiliated and stopped for 3 days a force of anywhere between 100,000 and 300,000 persians. So bad-ass by the american definition