Worst Collapses in Major Championship History

Rory McIlroy, 2011 Masters
Trying to become the second youngest player to win the Masters, McIlroy's four-shot lead at the start of the day quickly vanished, but he still went into the back nine tied for the lead. Then McIlroy tripled No. 10, four-putted for double bogey on No. 12, and when his tee shot found Rae's Creek on 13, his hopes for a green jacket were over.