bitch vs unpleasant person

bitch and unpleasant person both are nouns.

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

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

bitch: a person (usually but not necessarily a woman) who is thoroughly disliked
unpleasant person: a person who is not pleasant or agreeable

Other hypernyms of bitch include disagreeable person.

bitch (noun)	unpleasant person (noun)
female of any member of the dog family	a person who is not pleasant or agreeable
informal terms for objecting
a person (usually but not necessarily a woman) who is thoroughly disliked
an unpleasant difficulty

bitch (verb)	unpleasant person (verb)
say mean things
complain