Not every faction in every era needs to be challenging. As stated elsewhere, it can be a fine refreshment to take command of the English or Byzantines in early, knowing quite well that all of Europe will inevitably fall, and conquering and winning until your thirst is quenched.

Anyway, this thread is turning into the question of how to make factions harder instead of what factions are in fact hard to play.

Come on Caravel, what's yours?