lost cause 
noun
A person or thing that can no longer hope to succeed or be changed for the better: their opposition to planning for full employment was a lost cause he denied his drinking problem, and his friend left believing he was a lost cause...
- The plot itself is far from coherent and often meanders, but in a sense this fits with the characters it encapsulates: a bunch of lost causes fumbling their way through life in search of an unattainable salvation.
- St. Jude, the patron saint of lost causes, has received excessive attention from me recently, despite the fact that I am not Catholic.
- But I'm afraid I've never been one for lost causes.