You can delete your Veeam backup or immutable backup account from the dashboard. By doing so, all data is irreversibly deleted.

Remember that an immutable Veeam backup account, by the very definition of the service and as part of the security it provides, cannot be deleted if the immutability period defined for any of the copies has not yet expired. You can check in your Veeam console on which date this immutability will expire.