The phrase "an unequalled" is correct and usable in written English.
It can be used to describe something that is unmatched or unparalleled in quality or performance.
Example: "Her talent for painting is an unequalled gift that captivates everyone who sees her work."
Alternatives: "an unmatched" or "a peerless".
There was an unequalled year-long pilgrim age to commemorate its opening.
The Eastmans won out, at least with McCartney, and eventually made him an unequalled fortune.
For all of which reasons they occupy an unequalled position in the pantheon of design.
Bayly was a virtuoso historian, both prolific, writing a dozen influential books, and with an unequalled intellectual range.
Certainly national governments no longer have a monopoly of information, or an unequalled reach, compared to corporations and civil society.
"He is an extraordinary legislator with an unequalled record of achievements in the House of Representatives," he said.
Sealy's distinct technique and his singular meandering and descriptive narrative form have ensured him a unequalled standing in the predictable and often oversubscribed world of Indian writing in English.
Clough's spot-kick - after Mark Davies was fouled by George Thorne - prevented the Rams from winning a fifth straight home game without conceding a goal, a feat unequalled by Derby since 1925.
They sing, drink and laugh with an intensity unequalled in the West.
Drill in the modern sense was introduced by the Greeks, who periodically practiced the maneuvers of the phalanx; the Spartans carried disciplined drill to an extreme unequalled by their contemporaries.
Etretat, L'Aiguille et La Porte d'Aval, a view of a spectacular stretch of the Normandy coast that Monet drew in pastels in about 1885, illuminates the case for Monet as an unbeatable, unequalled artist whose popularity alone stops art snobs admitting that he is their favourite, too.
