How many indexed records have been the most indexed by a human since the beginning of FamilySearch?
I would be surprised if FamilySearch can supply a concrete answer to your question. Much indexing was done before computer indexing, by groups of church members. That would mean that "individual" records are probably not available for that time.
At first I thought your question was referring to the one person (not necessarily named) who had indexed more records than any other human. Now I am thinking that you might be using "human" in a plural sense - i.e., as opposed to the amount of records indexed by a machine.
Regardless, I think such stats - even if "available" - would probably be rather meaningless. Would they include, for example, multiple-indexed records for the exact same event, and/or relating to the exact same source?
Personally, I would fail to be impressed by any detailed numbers (I'm sure the figure would be in the billions, using whatever formula adopted) as surely the real issue with indexing is "quality over quantity".
There are surely millions of records that are now extremely difficult to find, following FamilySearch's auto-standardization exercise, as well as those that were originally transcribed so badly that they could never possibly be linked to the original subject of the event in question.
Or, reading the question another way, which single record has been indexed the most times - as in the baptisms that have been indexed 9 or 10 times each.
In any case, the indexed records of FamilySearch are only a small percentage of the total records held.
If you are asking how many names has one person indexed, I can tell you my mom indexed over 1 million names before she died in November 2024. :) I'm sure there were many people ready to thank her when she passed.