mortal sin vs wrath

mortal sin and wrath both are nouns.

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

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

mortal sin: an unpardonable sin entailing a total loss of grace
wrath: belligerence aroused by a real or supposed wrong (personified as one of the deadly sins)

mortal sin (noun)	wrath (noun)
an unpardonable sin entailing a total loss of grace	belligerence aroused by a real or supposed wrong (personified as one of the deadly sins)
	intense anger (usually on an epic scale)