Well, Marcus Tullius Cicero wasn't renowned for being "sexy", neither were
Scipio Africanus, Caius Julius Caesar, Marcus Aurelius, etc etc etc ...
So I can't quite pinpoint the correct term just now, though of course I will
think about it .... and let you know later on if I hit upon a suitable solution to
your problem :)

Venustus, cupidus, libidinosus, amatorius (said of a male)...OR venusta, cupida, libidinosa, amatoria (said of a female).

There are several varying shades of meaning, and no single Latin word does the multiple tasks of the English "sexy".

VENUSTUS: "beautiful, charming, blessed by the goddess Venus (and all the amorous/sexual possibilities associated with her)"

LIBIDINOSUS: "passionate, licentious, pleasure-seeking" (but not necessarily "good-looking" or "beautiful", but rather descriptive of behavior or character)

CUPIDUS: "desirous, attractive" (said of general wanting, desiring, etc.)

AMATORIUS: "amorous, ready to mate" (about behavior, and not necessarily about looks)