09:09 Nov 2 

Hi Cynthia,
I have posted below, in my Explanation Box, some information which may help you in choosing which among the three adjectives you may use. It seems that "unrivalled" should be it.

Pls note also that "ambassador nonpareil" is a standard term and has the most number of Google hits.

Have a nice day.

09:09 Oct 28 

You seem to be dumbfounded. Please try again.

00:56 Oct 28 

beyond compare, excellent, exceptional, ideal, inimitable, matchless, paramount, peerless, perfect, preeminent, sovereign, superior, supreme, surpassing, towering, transcendent, ultimate, unmatchable, unmatched, unparalleled, unsurpassable, outstanding, etc.

The only problem with posting so many options in one answer is that peers can't "officially" tell which one they like most. But everyone here do that too, including me. :-))