Whiner
Does anyone know a good phrase or term for a person who complains a lot about not getting their due? About life being unjust?
Whiner. Crybaby. Kvetcher. (Or, in some circles, client/customer/constituent/in-law/etc.)
'Whinger' is used pretty widely in the UK. Also 'stop whinging' etc
"Having a pity party" was popular in the U.S. a few years ago.