The literal answer to your question is Madagascar, a very large island off the coast of Africa which is about 3500 miles south (and 1100 miles to the east) of Greece. It is the largest island located south of Greece. I suspect, however, that what you are asking for the name of the largest of the Greek islands to the south of mainland Greece: that large island in the very south of Greece is Crete.
The island country of Cuba is the largest island south of Florida. Cuba is about 90 miles south of Florida, and this island is situated in the Caribbean.
Cuba is directly south of Key West. Key West is nearer to Cuba than to Florida.
cuba
cuba
Florida is farther south
Caiman Islands
Just south of the United States
Delaware, Flordia, Georgia, North Carolina, South Carolina, Virgina, Massachuettes, Rhode Island, New York, New Hampshire, Pennslyvania, Connetticut, New Jersey.
Gulf of Mexico
The largest social group in Florida is the SFYA (South Flordia Young Adults) they have over 3,700 members!
Bahia, also the largest state in the northeast region
The address of the Flordia Living History Inc is: 1960 Us Hwy 1 South Pmb 193, St Augustine, FL 32086-4233
It is 96.68 miles according to MapQuest.
Costa Rica is located south of Nicaragua and north of Panama.
Rakiura/Stewart Island. It is south of the South Island, and hence at a higher latitude.
Flordia