Try this…create a Task Report and indicate: Task Progress Status (Late), and then add any additional filters that you want such as Assignment Users, Project Status, etc. For columns, include Task Planned Completion Date, Task Actual Completion Date and then you can add a column for Week Day Difference to include the difference between the planned completion date and the actual completion date of the task.
Here is the text mode for that column - this was found on this Workfront Support article that provides some very helpful information: "https://support.workfront.com/hc/en-us/articles/360001028853-Understanding-Common-Uses-of-Text-Mode">Understanding Common Uses of Text Mode
displayname=Week Day Difference textmode=true valueexpression=WEEKDAYDIFF({plannedCompletionDate},{actualCompletionDate}) valueformat=HTML
One thing to keep in mind in this report...if you have 2 people assigned to the task and the task was due on August 3, and Person A finished their part on Aug 2 and Person B finished their part on Aug 16, then this task would show up on the report as "Late" by 9 days (even though Person A finished before the task planned completion date.) Hope this helps. Terry Hynd EBSCO Information Services