Using the query builder, I created a report that has a base resource type of Computer. I added the [Admin Group Members].[Member Name] field to it. I used a list of filter expressions to remove Administrator, and other admin groups that should be there by default as part of our process (like the IT Department, Domain Admins, etc.). When I run it, it gives me every machine, and who has admin rights to it.
You can also run the canned report - Reports/Discovery and Inventory/Inventory/Windows/Operating System/Count of Users with Admin Rights, which will give you the users that have admin rights and a number of systems on which they have admin rights on. You can drill down into those to see what individual systems they have rights to.