Unique values in group collection

Hello.

I have a collection that displays the results of employees' certifications.
The certificate shows the "position" where an employee can work.

One employee can have several result pass and not pass.

I need to display the last exam result based on position.

I have grouped the collection by "Position_certification":

ClearCollect(GroupedBy_Position, 
 GroupBy(
  CertificationList_coll,
  "Position_certification",
  "UserData"
));

And now I need to filter "UserData" so that only the latest and unique values by user`s email stay in.

In the end, I need a collection with all unique employees with their latest certification result

Could someone help with this challenge?