If you find duplicate participant responses on your list you can either select and delete them individually or use the dedupe feature in Ethnio by clicking on Responses >> List >> and the Dedupe icon.
Choose the column according to which you want to deduplicate, and then click Delete Duplicates.
For example, if you want to remove all duplicates with the same email address, add a check mark next to the email column and click delete. This will keep only the most recent data for participants. (Note: blank entries are included in the count.)