lion cub vs king of beasts

lion cub and king of beasts both are nouns.

Word	Noun	Adjective	Verb	Adverb
lion cub	Yes	No	No	No
king of beasts	Yes	No	No	No

As nouns, king of beasts is a hypernym of lion cub; that is, king of beasts is a word with a broader meaning than lion cub:

lion cub: a young lion
king of beasts: large gregarious predatory feline of Africa and India having a tawny coat with a shaggy mane in the male

Other hypernyms of lion cub include cub, young carnivore, lion, Panthera leo.

lion cub (noun)	king of beasts (noun)
a young lion	large gregarious predatory feline of Africa and India having a tawny coat with a shaggy mane in the male