Aaron Hernandez
This hype train came off the rails in the craziest way ever. Many NFL experts believed that Rob Gronkowski and Hernandez would be the greatest tight-end duo in history. They offered a unique threat and played brilliantly for the Patriots but then Hernandez killed people.

It’s one of the darkest NFL stories out there because of the horrific details. The Patriots disposed of him like yesterday’s garbage as soon as law enforcement charged him. Nobody expected them to stand behind a murderer so that’s not shocking. In the end, he took his own life in jail (via WBUR).