Use Overwrite option in Marketing Cloud Connector
|Knowledge Article Number||000213104|
You would like to select "Overwrite" as an option for an Import Activity from Salesforce Objects & Reports, however, the only options are "Add" and "Update," "Add only," and "Update Only."
To choose "Overwrite" from the Update Type drop-down box you first need to select and configure a Salesforce Object or Report. Overwrite will then become available.