legal opinion vs legal document

legal opinion and legal document both are nouns.

Word	Noun	Adjective	Verb	Adverb
legal opinion	Yes	No	No	No
legal document	Yes	No	No	No

As nouns, legal document is a hypernym of legal opinion; that is, legal document is a word with a broader meaning than legal opinion:

legal opinion: the legal document stating the reasons for a judicial decision
legal document: (law) a document that states some contractual relationship or grants some right

Other hypernyms of legal opinion include instrument, legal instrument, official document.

legal opinion (noun)	legal document (noun)
the legal document stating the reasons for a judicial decision	(law) a document that states some contractual relationship or grants some right