How can a contact unsubscribe from my list?
Every message sent via GetResponse contains an unsubscribe link at the bottom. Below you can find an example of the GetResponse disclaimer:

The recipient clicks the link and sees an unsubscribe page with a list of all lists they are subscribed to. Then they can pick one or more lists they wish to unsubscribe from, or they can stay on all lists and just withdraw their consent status.

After unsubscribing, they will also be able to select a reason for it, which is also described here.

To find contacts who unsubscribed this way, you can use the Advanced search option on Search contacts page:
- Go to Contacts > Search and click Advanced search.
- Select Add condition and choose Contacts actions > Unsubscribes and select the option for removal.