You want to use the "Run report multple times" feature.
Step 1: Create a query on summary data that contains username and hits, sorted by hits descending.
Step 2: Create a query that has category and hits, sorted by hits descending
Step 3: Create an advanced report.
- The report body will have the query in step 2.
- On the advanced tab, check the box for "run report mulitple times", then select the username from your query in step 1
- Don't forget to set filters for the user query, such as date range or group membership, etc.
- set your date range and filters for the main report.
What happens is that Web Reporter will run your user query to get the list of user names, then run the main report several times with a user filter from the user query.