No? Kurapika's Specialist ability allows him to use all of his other Nen classes at maximum efficiency and that's unique to Kurapika because he's part of the Kurta clan.
Every Specialist ability is different. Alluka's Specialist ability, for example, isn't combat-based at all, so it's impossible to say the Specialist class is the best out of all the Nen classes.
I was not aware Alluka was a specialist. Dont recall that being mentioned. Also I recall that being a specialist does allows you to master any other nen class you want. Kurapika was a different case. His ability lets him master all other nen classes it an instant. For a regular specialist it just means that you dont exhaust your potential when learning a different kind of ability (Like that guy who created a clone of himself when he fought Hisoka).
And actually it really isnt impossible to say they are the best. We never found out what the kings ability fell under. By absorbing other nen users he was able to exponentially grow in power. I would assume his ability would fall under specialist as well. Hes the strongest being weve seen thus far so yeah. I still think specialist are the rarest and most gifted.
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There you go.
About that specialist thing, I heard that it wasn't in the viz translation.
All that talks about is old man Netero. He was a emission type.
But in the manga as I posted it said Beyond was a specialist. Until we get any other evidence that he is an enhancer as other have stated, this is a close to what his power is in what we have so ill believe he is specialist until proven otherwise.