There is no tool that exists that outputs all records that are duplicates (those sharing the selected values with at least one other record) and also outputs the records that are not duplicates (those not sharing the selected values with at least one other record).
The Unique Tool is not sufficient. It only provides the first record of a unique duplicate group along with any non-duplicates and then provides a secondary output that only contains the additional records of a duplicate group. Sometimes you only care about the duplicates and want to quickly see what differs between the unique groups.
For example, if there are 4 records with the City of Austin and I am looking for duplicates on City I want to see all 4 records with Austin in the output so I can quickly compare additional fields to see what might differ, or if they are all indeed truly duplicates.