General synonyms:
* Pointless: This is a straightforward synonym that emphasizes the lack of purpose or effectiveness.
* Useless: This emphasizes the inability to produce any desired result.
* Vain: This highlights the effort put in despite the lack of success.
* Fruitless: This implies a lack of any positive outcome.
* Hopeless: This emphasizes the lack of possibility for success.
More specific synonyms:
* Abortive: This implies a premature or unsuccessful attempt.
* Unproductive: This emphasizes the lack of any beneficial outcome.
* Ineffectual: This highlights the lack of power or influence.
* Worthless: This conveys a complete lack of value or worth.
* Unsuccessful: This is a general term for a lack of achievement.
Formal synonyms:
* Otiose: This suggests something useless or pointless.
* Nugatory: This emphasizes the insignificance or worthlessness of something.
* Bootless: This emphasizes the lack of any benefit or profit.
The best synonym for "futile" will depend on the specific context and the desired level of formality.