Apollo Restores Rather Than Creates New Contacts
If you delete a contact in Apollo that was initially created from SFDC sync (pull), manually pulling that contact/lead from SFDC will restore the previously deleted Apollo Contact. In other words, rather than creating a new Apollo Contact, we'll restore the matching deleted one if it's the same Salesforce Contact.
You can confirm if an Apollo Contact was created in Apollo, via CSV upload, or via your CRM (Salesforce) integration by scrolling to the bottom of any Apollo Contact Profile's Activity list:
Similarly, if you update a SFDC contact/lead that has been deleted in Apollo, we will restore and update the original Apollo contact, rather than creating a brand new one.
If you've deleted a set of Contacts from Apollo and want to re-sync your Apollo Contact List with your current database of Contacts/Leads in Salesforce, navigate to Settings>Integrations>Salesforce>Contacts and click Pull all Salesforce Leads/Contacts to Apollo Contacts. While you're there, be sure you have the switch ON to Show Salesforce leads/contacts on Apollo's Contacts tab: