You can't use an email template condition to detect when a recipient forwards an email and hide the unsubscribe link afterward. The template renders when the email is sent, while forwarding happens later in the recipient's email client.
Understand why forwarded email detection doesn't work
Template conditions run when the original email is generated and sent. When a recipient forwards the message, their email client creates a new message from the existing content. The sending platform doesn't render the original template again, so it can't receive a forwarded status.
Prefixes such as Fwd: and generic email headers aren't reliable because email clients can change, remove, or omit them.
Keep the unsubscribe link available
Keep the unsubscribe or preference-management link in the original marketing email. In Bloomreach, you can use {{ consent.page }} to generate the recipient's consent-page link.
One-click unsubscribe is a separate mechanism handled through email headers and supported email clients. It is not a replacement for the link in the email body. Neither mechanism detects forwarding or hides content in forwarded copies.
If you need to restrict access to sensitive content, host it behind an authenticated web page rather than relying on HTML in email to hide it after forwarding.