Which Greek stronghold with Catholic administration was the last to survive the Ottoman conquest: Crete, Cyprus or other?

As I pointed out in commenting Niko Vasileas’ answer, the Morea was reconquered by the Venetians after close to two centuries of Ottoman rule, whereas Tinos was under continuous Venetian rule right through to 1715.

Add to this the odd situation of the Ionian Islands. They remained under Venice until 1797. Then they fell under a sequence of regimes:

• The French departments of Greece (i.e. Napoleonic France)
• 1800: The Septinsular Republic, a Russian–Ottoman condominium
• 1807: The United States of the Ionian Islands, a British protectorate
• 1864: The Kingdom of Greece

Now if you count Napoleonic France as Catholic (I’m wary of doing so), the last Catholic administration of Greek territory ended in 1800. Then again, that assumes the Septinsular Republic was part of the Ottoman conquest: I don’t get the impression there was much of an Ottoman presence in the condominium at all, and Greek-language self rule by aristocrats is not quite the same as the Millet (Ottoman Empire).

That’s why most people would not even consider the Ionian islands for this answer: they never were really ruled by the Ottomans.