loup-garou vs mythical monster

loup-garou and mythical monster both are nouns.

Word	Noun	Adjective	Verb	Adverb
loup-garou	Yes	No	No	No
mythical monster	Yes	No	No	No

As nouns, mythical monster is a hypernym of loup-garou; that is, mythical monster is a word with a broader meaning than loup-garou:

loup-garou: a monster able to change appearance from human to wolf and back again
mythical monster: a monster renowned in folklore and myth

Other hypernyms of loup-garou include mythical creature.

loup-garou (noun)	mythical monster (noun)
a monster able to change appearance from human to wolf and back again	a monster renowned in folklore and myth