piece de resistance vs oddity

piece de resistance and oddity both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece de resistance	Yes	No	No	No
oddity	Yes	No	No	No

As nouns, oddity is a hypernym of piece de resistance; that is, oddity is a word with a broader meaning than piece de resistance:

piece de resistance: the outstanding item (the prize piece or main exhibit) in a collection
oddity: something unusual -- perhaps worthy of collecting

Other hypernyms of piece de resistance include curio, curiosity, oddment, peculiarity, rarity.

piece de resistance (noun)	oddity (noun)
the outstanding item (the prize piece or main exhibit) in a collection	something unusual -- perhaps worthy of collecting
the most important dish of a meal	a strange attitude or habit
	eccentricity that is not easily explained