Manchester United 1 - 6 Manchester City
Not actually a thrashing on the scale of the others in this list with the margin of victory only five goals. But it was most certainly a drubbing, and a shock one at that. And its significance was huge.
City had been threatening to come good for a few of seasons since 2008 when they had been bought by the Abu Dhabi United Group. And it was this game in October 2011 that signalled their arrival as genuine title contenders.
A complete annihilation of their neighbours away from home, they scored three goals in stoppage time to complete the rout.
They would go on to win their first Premier League title - beating United into second on goal difference.