unconvincing vs unbelievable

unconvincing and unbelievable both are adjectives.

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

As adjectives, unconvincing and unbelievable are synonyms defined as:

unconvincing and unbelievable: having a probability too low to inspire belief

Other synonyms of unconvincing include improbable, unlikely.

unconvincing (adjective)	unbelievable (adjective)
not convincing	beyond belief or understanding
having a probability too low to inspire belief	having a probability too low to inspire belief