Matt,

I would do this in 2 steps.

First, make a query that will return a complete list of all Competencies
for all Employees.  The SQL of such a query will look something like this...
 SELECT [Employee Name].[Employee ID], Competencies.[Competencies ID]
 FROM [Employee Name], Competencies

Then, make another query using this first query, plus the Completed
Tasks table, to give you those uncompleted competencies.  The SQL of
such a query will look something like this...
 SELECT [YourFirstQuery].[Employee ID], [YourFirstQuery].[Competencies ID]
 FROM [YourFirstQuery] LEFT JOIN [Completed Tasks]
   ON [YourFirstQuery].[Employee ID]=[Completed Tasks].[Employee ID]
   AND [YourFirstQuery].[Competencies ID]=[Completed
Tasks].[Competencies ID]
 WHERE [Completed Tasks].[Compeleted task id] Is Null

Well, in practice, you would probable also want to include the [Employee
Name] table and the Competencies table into this second query, so that
you can return the actual name of the enployee, and the name of the
competency, but I tried to keep it simple for starter.