Here is the an example of how to create a report comparing donors in two campaigns.

1. Create a Gift Report.  Using the blue filter button choose a date range that includes both campaigns and then the actual campaigns you want to compare.  In my example I chose GHD 2020 and GHD 2021.
2. Then click Run Report. Once the report is complete you will group by Display Name.  You can do this by dragging the Display Name column up into the grouping header.
Note:  We recommend hiding any unwanted columns by clicking on the three dots in any column and hiding or checking the data you would like to see.  
By grouping by the Display Name you will be able to see what donors gave to either campaign or both.
3. SAVE and name your report for use in the future.