Previously, to unsubscribe contacts from all mailings, you'd need to do it on a contact-by-contact basis.
Now you can mass-unsubscribe contacts from all mailings
Go to your Contacts page:
1/ Filter the contacts that you want to unsubscribe.
2/ Select [Bulk Actions] -> [Unsubscribe]:
3/ Choose [Unsubscribe from all mailings] -> [Unsubscribe]: