critter vs beast

critter and beast both are nouns.

Word	Noun	Adjective	Verb	Adverb
critter	Yes	No	No	No
beast	Yes	No	No	No

As nouns, beast is a hypernym of critter; that is, beast is a word with a broader meaning than critter:

Other hypernyms of critter include animal, animate being, brute, creature, fauna.

critter (noun)	beast (noun)
a regional term for `creature' (especially for domestic animals)	a living organism characterized by voluntary movement
	a cruelly rapacious person