mortal sin vs superbia

mortal sin and superbia both are nouns.

Word	Noun	Adjective	Verb	Adverb
mortal sin	Yes	No	No	No
superbia	Yes	No	No	No

As nouns, superbia is a hyponym of mortal sin; that is, superbia is a word with a more specific, narrower meaning than mortal sin:

mortal sin: an unpardonable sin entailing a total loss of grace
superbia: unreasonable and inordinate self-esteem (personified as one of the deadly sins)

mortal sin (noun)	superbia (noun)
an unpardonable sin entailing a total loss of grace	unreasonable and inordinate self-esteem (personified as one of the deadly sins)