From Longman Dictionary of Contemporary Englishprofessional liar/complainer etcprofessional liar/complainer etcTOO/TOO MUCHsomeone who lies or complains too much – used humorously → professional
Examples from the Corpus
professional liar/complainer etc• Maurice breaks his promises so consistently that he begins to seem a professional liar.• He's a professional complainer - I've encountered hundreds of them in my time. 