Unhelpfulness is the noun for the quality of not helping — the state or habit of being unhelpful. It names the thing itself rather than describing a person or an action, which is why it turns up most in complaints, reports and formal writing: I want to complain about the unhelpfulness of your staff. It is uncountable — you never say "an unhelpfulness" or "two unhelpfulnesses". It works with of (the unhelpfulness of the reply), with a possessive (his unhelpfulness), or on its own (the unhelpfulness was breathtaking). Two things are worth knowing. First, this is a heavy, formal-feeling word, and quite long — five syllables. In everyday speech, English speakers almost always avoid it and rearrange the sentence to use the adjective instead: rather than "his unhelpfulness annoyed me", people say "he was so unhelpful". Choosing the noun makes you sound official, which is exactly why it is useful in a written complaint and slightly odd in conversation. Second, it is not neutral. It quietly suggests that the person could have helped and chose not to — that is why it stings more than simply saying someone did not help.

不幫忙、幫倒忙（這種態度或行為）。是抽象名詞，語氣正式，常用在客訴或書面抱怨：「貴公司人員的不友善與推託」。