Deleting a contact in Engage is done through the /contacts endpoint using the contactId:
DELETE /api/v3/contacts/[contactId]
source parameter to show how the contact was deleted. While it’s not mandatory, it is useful for tracking the reason why contacts were deleted.
This gives extra information about why the contact was deleted. Example values are “POS” or “e-com” but you can send anything else you want.
This endpoint is not to be used for batch deletion. For mass deletion of contacts, use the Engage UI or bulk integrations methods (see this section). Responses
A successful deletion will return HTTP 200 Ok.
If a contact with that ID could not be found, or was already deleted, you’ll get HTTP 404 Not Found. 
