#1 Manchester United 1 Manchester City 6 (October 2011)
For someone stating this result was the most embarrassing defeat in the past decade is one statement, but if you wholeheartedly said it was the most humiliating in the history of Manchester United, would you be wrong?
Roberto Mancini took his in-form City side to the 'Theatre of Dreams' following an impressive start to the 2011/2012. Both sides were set to battle it out after each team picked up 20 points from 8 games - in comparison to 22 from 8 matches from the visitors.
(Video Courtesy: JustFootball YouTube Channel)
The Red Devils succumbed to the biggest annihilation ever witnessed at Old Trafford in the Premier League era as Mario Balotelli, and Edin Dzeko scored a brace each, while goals from Sergio Aguero and Joleon Lescott further added to Sir Alex Ferguson's misery. A solitary goal from Darren Fletcher (arguably the best of the contest) didn't spare the blushes of the 76,000 in attendance.
The result proved crucial at the end of the season, as City won the Premier League title on goal difference.