I have a feeling, just based on how law works, that this will be highly subjective. I interpret your question as being about skill. If that’s not what you mean please correct me. (Sorry for the non-answer)

Even within criminal law, things like acquittal rate would very with the exact kind of practice - a guy that specialises in complex white-collar crime and takes easy cases might get a really good one without too much skill. Someone who takes anybody who will pay upfront will probably have a cruddy one. This could get even more extreme if you look at non-Western or historical systems where the result is almost guaranteed in advance. So, that’s not in the spirit of the question.

I seem to remember an XKCD What If where Randall Munroe mentions the highest paid (criminal?) attorney in the US, but there again, it was someone who sounded highly connected. Does that correspond to skill? (Edit: The late Ted Olson, who does appear to have defended criminal cases)

Somebody that actually knows a lot of names and legal history might be able to tell you something more useful, but just take it with a grain of salt.