Summary Report with zero assessments

I'm assuming you have a one-many relationship here, with Consultants having many Assessments. 

It sounds like what you want is a summary field, which you can then use to filter a regular report. You can set up a summary field called # of Assessments on the consultants table to count all related assessments. Then, you can simply filter any report to only include consultants where # of assessments = 0