unbelievable vs dumbfounding

unbelievable and dumbfounding both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unbelievable	No	Yes	No	No
dumbfounding	No	Yes	No	No

unbelievable (adjective)	dumbfounding (adjective)
beyond belief or understanding	bewildering or striking dumb with wonder
having a probability too low to inspire belief