Pythian Games vs agon

Pythian Games and agon both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pythian Games	Yes	No	No	No
agon	Yes	No	No	No

As nouns, agon is a hypernym of Pythian Games; that is, agon is a word with a broader meaning than Pythian Games:

Pythian Games: the ancient Panhellenic celebration at Delphi held every four years in the third year of the Olympiad in honor of Apollo
agon: a festivity in ancient Greece at which competitors contended for prizes

Pythian Games (noun)	agon (noun)
the ancient Panhellenic celebration at Delphi held every four years in the third year of the Olympiad in honor of Apollo	a festivity in ancient Greece at which competitors contended for prizes