overemphasis vs emphasis

overemphasis and emphasis both are nouns.

Word	Noun	Adjective	Verb	Adverb
overemphasis	Yes	No	No	No
emphasis	Yes	No	No	No

As nouns, emphasis is a hypernym of overemphasis; that is, emphasis is a word with a broader meaning than overemphasis:

Other hypernyms of overemphasis include vehemence.

overemphasis (noun)	emphasis (noun)
too much emphasis	intensity or forcefulness of expression
	the relative prominence of a syllable or musical note (especially with regard to stress or pitch)
	special and significant stress by means of position or repetition e.g.
	special importance or significance