monster vs unpleasant person

monster and unpleasant person both are nouns.

Word	Noun	Adjective	Verb	Adverb
monster	Yes	No	No	No
unpleasant person	Yes	No	No	No

As nouns, unpleasant person is a hypernym of monster; that is, unpleasant person is a word with a broader meaning than monster:

Other hypernyms of monster include disagreeable person.

monster (noun)	unpleasant person (noun)
(medicine) a grossly malformed and usually nonviable fetus	a person who is not pleasant or agreeable
a cruel wicked and inhuman person
a person or animal that is markedly unusual or deformed
an imaginary creature usually having various human and animal parts
someone that is abnormally large and powerful