Deleting a Data Extension
We often hear from users who are trying to delete a data extension but can't seem to do so successfully even when using the "delete" option. Why? Marketing Cloud is tricky in this regard; to successfully delete a data extension from your business unit, you have to complete the deletion in two separate locations.
Step One: Delete from Import Menu
To delete a data extension from the import menu, login to Marketing Cloud and navigate to Email Studio - Interactions - Import.
Locate the data extension you want to delete, click the checkbox next to its name, and then select Delete from the menu.

Step Two: Delete from Salesforce Data Extensions Menu
Next, still in Email Studio, navigate to Subscribers - Salesforce Data Extensions.

Use the Search tool to locate the data extension you want to delete. Then, click the checkbox next to it and click Delete from the menu.

Your data extension will then be removed from your Marketing Cloud business unit.