Sure, lots of ways.
What would you like to do with them?
First, you need to define "Bad Leads" which could be people w/o data, people who haven't been updated in 18 months, etc...people with no activity since 6 months ago...
Then you can run a batch campaign to delete them from SFDC and/or Marketo. You should probably archive them by exporting that list FIRST...just in case. Be sure this isn't going to throw off your reports.
For Unsubscribes you can send them to a special Queue. But you might want to be careful. Just because they unsub doesn't mean they are a bad prospect for sales. Usually people deduct points for unsubs.
You should also monitor repeated hard bounces and place those on to Email Invalid or Bad Leads eventually because they will start to affect your email rep.