4. Jeff Skilling
Jeff Skilling had the lucrative position of CEO of Enron Corp., giving him access to a wide network of people and operations in natural gas markets. In 2001, it came to light that the company, long considered a poster boy for running a profitable business had been committing fraud the whole time.
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They used a series of accounting loopholes and corruption to hide billions in revenue and even more in debt. The scheme was so complex that it needs a whole novel to detail down in full. Skrilling has been in prison since 2006, slated for release in 2019.