It is a variety that you have poorly identified with low quality sweet wines. Mavrodaphne makes some of the most interesting dry red wines you can taste.
If you must know only one Greek variety, then this should be definitely Assyrtiko! Learn everything you need to know about the landmark variety of the Greek vineyard!
If you need to know two Greek varieties, Agiorgitiko is definitely one of them! Learn everything you need for the landmark variety of the Greek vineyard!