For the Ultimate Underdog, no one could have predicted the events that transpired at The Great American Bash in July 2006. For three months, then-World Champion Rey Mysterio was at the top of his game – that is, until one of his dearest friends robbed him of the dream that had taken him 16 long years to achieve.

Kicking off this edition of "List This!", Chavo Guerrero’s actions against the friend he once considered a hermano, costing Rey Mysterio to lose his coveted gold, is WWE.com's No. 10 Hardest Hitting Betrayal.

Guerrero, then retired, had shown up in Mysterio's corner at The Great American Bash as Rey defended the World Championship against King Booker. He had been the champion’s most vocal supporter ever since Mysterio had pinned Randy Orton to win the gold at WrestleMania 22. Since the Ultimate Underdog's victory, they had honored Eddie Guerrero's memory together – and together, they vowed to keep the dream alive by any means necessary.

As the champ and his royal challenger battled over WWE’s top prize at the site of Mysterio’s first WWE contest and Eddie Guerrero’s final match – the Conseco Fieldhouse in Indianapolis – the self-proclaimed “Mexican Warrior” shocked the WWE Universe by leveling his friend with a steel chair just as it looked like Mysterio might retain his gold. Guerrero’s ultimate bash of betrayal not only brought the champion’s reign to a sudden halt, but also crushed a friendship that seemed indestructible.

Guerrero claimed his ruthless actions were provoked by Mysterio being a “thief.” He accused his long-time friend of stealing his spotlight as well the “memory of Eddie [Guerrero].” He also called the former World Heavyweight Champion a “leech” who had been living off the Guerrero name.

Knowing exactly how to strike Rey Mysterio where it would hurt most, Chavo Guerrero did precisely that on July 23, 2006, catapulting a long series of brutal confrontations between himself, Vickie Guerrero and the Master of the 619 – and leaving the Ultimate Underdog with painful memories neither he nor our fans will ever forget.