Worst bust? ... a good case can be made for several players.
Honorable mentions:
Skyler Green - For a guy drafted to return punts, he showed virtually no knack for it. He was such a bust that he lasted only a couple of months.
Isiah Stanback - The front office, media, and many fans were giggling like lovestruck school girls when the Cowboys "stole" Isiah in the 4th round. He is the single most overhyped 4th round draft pick in the history of the Dallas Cowboys. If not for one small detail, he could have become the next Jerry Rice. The detail? He couldn't play the position.
Qunicy Carter - If you find a guy with a murky history and poor accuracy, draft him several rounds before anybody else would, with the intention of him instantly becoming your franchise QB - we've got a clear "bust" in the making. Obviously Carter didn't live up to Jerry's unreasonable expectations. But who is the bust here? Carter, for snorting away his mediocre career, or Jerry, for believing that an inaccurate, mediocre snorter could be his franchise QB?
Jacob Rogers - The franchise needed him to become at least a serviceable player, but he didn't.
but the biggest draft bust of the decade is:
Bobby Carpenter - The 18th pick in the NFL draft has to be more than a good kick coverage player. That Carpenter is now playing 3rd downs is an accident of timing - Kevin Burnett decided to move to San Diego before younger replacements were healthy and ready. Carpenter is stop gap, and you need for your mid-1st round draft pick to develop into more than just a stop gap player.