There are 2 ways to delete a contact

Option 1- https://api.brevo.com/v3/contacts/{identifier}

Option 2- https://api.brevo.com/v3/contacts/{identifier}?identifierType={}

Option 1 only works if identifierType is email_id (for EMAIL) or contact_id (for ID of the contact),where you can directly pass the value of EMAIL and ID of the contact.

Option 2 works for all identifierType, use email_id for EMAIL attribute, contact_id for ID of the contact, ext_id for EXT_ID attribute, phone_id for SMS attribute, whatsapp_id for WHATSAPP attribute, landline_number_id for LANDLINE_NUMBER attribute.