How many fields are required to make it a unique record?
If only one, add a group for that field and move the fields you want to show up on the report to the group header or footer. The header will show the first record in the group, the footer will show the last record in the group.
If there is more than one field, you can either add groups for each field, like above, or create a formula field that concatenates the fields together. Create a group on that field and move the detail to the header/footer. That will eliminate your duplicates.