I've been pretty much insta-routed about a dozen times over several campaigns by the Timurid elephants and their dread Generals.

Assaulted Milan once as the Turks on Jihad, and got a large army wiped out when assaulting the walls by a pretty small number of Dismounted Feudal Knights and Pavise Xbows.

And some embarassing defeats in the New World with Scottish and Venetian armies. Sorted that since going the Byzantines though.

Thats about it...