tenderness vs soft spot

tenderness and soft spot both are nouns.

Word	Noun	Adjective	Verb	Adverb
tenderness	Yes	No	No	No
soft spot	Yes	No	No	No

As nouns, soft spot is a hyponym of tenderness; that is, soft spot is a word with a more specific, narrower meaning than tenderness:

Other hyponyms of tenderness include attachment, fond regard, protectiveness, regard, respect.

tenderness (noun)	soft spot (noun)
a tendency to express warm and affectionate feeling	a place of especial vulnerability
a feeling of concern for the welfare of someone (especially someone defenseless)	any membranous gap between the bones of the cranium in an infant or fetus
a positive feeling of liking	a sentimental affection
warm compassionate feelings
a pain that is felt (as when the area is touched)