pitfall vs difficultness

pitfall and difficultness both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitfall	Yes	No	No	No
difficultness	Yes	No	No	No

As nouns, difficultness is a hypernym of pitfall; that is, difficultness is a word with a broader meaning than pitfall:

pitfall: an unforeseen or unexpected or surprising difficulty
difficultness: the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result

Other hypernyms of pitfall include difficulty.

pitfall (noun)	difficultness (noun)
a trap in the form of a concealed hole	the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result
an unforeseen or unexpected or surprising difficulty