"unrivalled knowledge" is correct and usable in written English.
You can use it to refer to someone or something that has an exceptionally high level of knowledge. For example, "The professor's unrivalled knowledge of ancient history was evident in every lecture."
Cassy said: "Melvyn has an infectious enthusiasm for and an unrivalled knowledge of the arts in all its guises.
Tomalin doesn't hesitate to condemn Dickens when his behaviour demands it, yet she writes throughout with great sympathy and unrivalled knowledge in the most limpid and stylish prose.
"From the trust's inception, Patricia has consistently and courageously applied her unrivalled knowledge and experience to its work," said BBC Trust chairman, Lord Patten, said.
Our readers are hungry for more of our unique, independent culture coverage and Nigel is the perfect fit - bringing unrivalled knowledge of the entertainment industry.
She shared her unrivalled knowledge of St Ives's artistic heritage with characteristic generosity and was modest about her achievements; perhaps too modest, sometimes.
A franchise for BDB would leave BSkyB in effective control of two of the three main sorts of digital television, and with an unrivalled knowledge of the names and addresses of subscribers.
Once she moved to America she kept fans enthralled with unrivalled insider knowledge of Hollywood.
This, from a man whose unrivalled legal knowledge, and rapier-sharp mind both awed and occasionally unsettled his legal contemporaries.
She gave millions of her readers an unrivalled inside knowledge of Hollywood and the glamorous lives of the rich, famous and infamous.
His first novel, Head of State, is being trailed as a political thriller "making full use of his unrivalled inside knowledge": "While the United Kingdom approaches a crucial and delicately-balanced referendum on Europe, a group of ruthlessly determined individuals will stop at nothing – including murder – to prevent the truth from getting out".
Ordinary tragedies are magnified into unrivalled dramas by the knowledge of how they feed into the Beatles' myth – most notably in the case of John Lennon's mother, Julia.
