There is no clear-cut answer to this question as "best" is a highly subjective term. Some factors you may want to consider when comparing health insurance TPAs (Third Party Administrators) include their financial stability, claim processing efficiency, customer service, and the types of plans they offer.
Some popular health insurance TPAs in India are Apollo Munich, Bajaj Allianz, Max Bupa, HDFC Ergo, and Religare. You can read more about them and get quotes on PolicyBazaar.com.