controversy vs difference

controversy and difference both are nouns.

Word	Noun	Adjective	Verb	Adverb
controversy	Yes	No	No	No
difference	Yes	No	No	No

As nouns, difference is a hypernym of controversy; that is, difference is a word with a broader meaning than controversy:

controversy: a contentious speech act; a dispute where there is strong disagreement
difference: a disagreement or argument about something important

Other hypernyms of controversy include conflict, difference of opinion, dispute.

controversy (noun)	difference (noun)
a contentious speech act; a dispute where there is strong disagreement	the quality of being unlike or dissimilar
	a disagreement or argument about something important
	a variation that deviates from the standard or norm
	the number that remains after subtraction; the number that when added to the subtrahend gives the minuend
	a significant change