Here I would like people to share any bad calls.
Mine happened when I played the expert Spanish in 1440 (more or less). By then most of Europe had been conquered, only sporadic provinces left which I devoured one by one at leisure, basking in the rays of my own vanity. Then it seemed to me that my aged king was bored in his lofty citadel deprived of deeds of arms. So I decided to entertain and exercise him sending him to capture Crete (from Italians, I guess) and leaving his son as a steward. He did capture Crete inadvertently destroying the port. Being cut off from the monarch the whole empire was wrecked by rebellions. The labor which had taken 400 years to almost accomplish went down the drain. I even saw the Swiss appear (for the first time in all my games). I must confess, I had bad dreams that night. At first I tried to hold on to every province I could, but soon abandoned it as hopeless. Instead, I withdrew all my troops to the limited number of loyal provinces (about 10 or 12) and waited four years for the port to be built. When it was ready I surprisingly quickly retrieved the lost provinces and left only the Swiss besieged in Swabia when the clock struck 1453. So all was well that ended well. But I still don't relish the emotions I had and the names I called myself for that wildgoose chase in Crete.