Title - Remove Unsubscribe Text From the"Admin - https://nation.marketo.com/docs/DOC-1114
If you remove the text at the Admin level (as per the documentation), this will immediately apply to all emails created (including: active, inactive). You are not required to re-approve your previously approved emails once this change has been saved in the Admin -> Email settings.
All pre-existing emails will replace the default "Unsubscribe" text at the bottom of all emails, after changes have been saved in Admin -> Email settings.
After removing the default "Unsubscribe" text from emails, you should replace it with a Custom Unsubscribe option. This is in order to remain compliant with the Can-Spam Act.