Fail is a pretty popular term on the internet these days, and one I'm quite fond of.
Looking in my Chinese dictionary I can't find a great equivalent - is there a good way to say this? What would be the best word to use?
I would suggest "悲剧" (mainland China).
"悲剧" literally means "tragedy". When you "fail" to do something it's really a tragedy (haha).
This usage gained popularity in recent years among mainland Chinese Internet users.
I think "悲剧" is a better translation of "fail" compared with "囧". I use "囧" when I'm embarrassed or frustrated, similar to "呃" and "无语". "囧" as a slang term has the same meaning as "窘" in "窘迫" (uneasy).