Google & Microsoft
• Disconnect in your Multical account settings — tokens deleted immediately from the database
• Or revoke in Google Account settings (myaccount.google.com › Security › Third-party apps)
• Or revoke in Microsoft Account settings (account.microsoft.com › Privacy › Apps & services)
Apple
• Disconnect in your Multical account settings — encrypted credentials deleted immediately from the database
• Or revoke the app-specific password in your Apple ID settings (appleid.apple.com › Sign-In and Security › App-Specific Passwords)
• For iCal URL connections: disconnect in Multical settings, or simply stop sharing the calendar link in your Apple Calendar app