Negative (Null) Reporting

I'm looking to create an Activities report where the activity must have an Account or a Contact while including Opportunity fields. My result set so far includes some duplicates, e.g. activities that have an account with no contact and an opportunity name - these same records come back without the opportunity name causing duplicates. The current report is made up of 5 negative (null) subreports at this point.

Any suggestions, thoughts on how to eliminate these duplicate records? The ones with the Opportunity Name are the ones to keep, the duplicates without the Oppty Name should be removed.

Thanks.