Ryan Leaf
A loud minority of NFL ‘experts’ said that Leaf had a higher long-term upside than Peyton Manning in 1998. San Diego made him the second-overall pick after an excellent season with the Cougars. They traded the house for the quarterback because they believed he’d lead them to the promised land.

However, Leaf had massive problems with his maturity and substance abuse. He argued with the media and drank like a fish. In the end, he crashed out of the league as one of the biggest busts ever. Leaf had so much potential but in the end, it was too good to be true. He even spent time in jail for various petty crimes (via Sportskeeda).