Here are some synonyms for "unrivaled":
* Unequalled
* Unmatched
* Peerless
* Supreme
* Unsurpassed
* Incomparable
Example sentences:
* "The singer's voice is unrivaled in the industry."
* "The company's customer service is unrivaled."
* "The view from the mountaintop is unrivaled."
Essentially, "unrivaled" implies that something is so good or exceptional that there is nothing else that can compare to it.