grumbler vs disagreeable person

grumbler and disagreeable person both are nouns.

Word	Noun	Adjective	Verb	Adverb
grumbler	Yes	No	No	No
disagreeable person	Yes	No	No	No

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

Other hypernyms of grumbler include unpleasant person.

grumbler (noun)	disagreeable person (noun)
a person given to excessive complaints and crying and whining	a person who is not pleasant or agreeable