I actually don't think Sanji vs King was that crazy even if if i didn't believe it. It was possible if we imagined Zoro was going to 2 vs 1 Kaido with Luffy.
To me Sanji vs Katakuri was much worse
I would bet an arm that Sanji admiral opponent if he gets one is Ryokugyu
Aramaki isn't even threatening solely because he's got strong offense like most other Admirals, he's just annoying as fuck and tricky with his fruit.
He tries to restrain you with plants, drain the water in your body, etc.
But yes, in that case, I would argue Sanji is his best opponent. Kizaru and Fujitora would be Zoro's and Akainu would be Sabo's or Luffy's.