During his reign, Giancana was one of the richest and most powerful people in the world, and for over two decades, he was a multi-billionaire, his greatest net worth was a jaw-dropping $12 billion. is regarded by the FBI and Chicago law enforcement as one of the most powerful criminals of all time. He is arguably the most powerful mob boss in American history, but unquestionably one of the most powerful and dangerous crime lords of all time.