carnal abuse vs sex activity

carnal abuse and sex activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
carnal abuse	Yes	No	No	No
sex activity	Yes	No	No	No

As nouns, sex activity is a hypernym of carnal abuse; that is, sex activity is a word with a broader meaning than carnal abuse:

carnal abuse: any lascivious contact by an adult with the sexual organs of a child (especially not involving sexual intercourse)
sex activity: activities associated with sexual intercourse

Other hypernyms of carnal abuse include sex, sexual activity, sexual practice.

carnal abuse (noun)	sex activity (noun)
sexual intercourse with a person (girl or boy) who has not reached the age of consent (even if both parties participate willingly)	activities associated with sexual intercourse
any lascivious contact by an adult with the sexual organs of a child (especially not involving sexual intercourse)