@Bgood - Unfortunately, looking at the list of Events documented below, I don’t think there is a native Bigcommerce Klaviyo event for when an order is Delivered. 

• Reviewing Your BigCommerce Data

It seems like the last Event in a normal order flow sent to Klaviyo is Fulfilled Order. 

If you’re open to using a third party app, and you are using one of their supported carriers, I highly recommend Aftership which has a native integration with Klaviyo here:

• Klaviyo Aftership
• How to Integrate with AfterShip

Aftership sends all carrier events to Klaviyo where you can trigger additional Flows and messages, including delays, in transit, and delivered notification.  

Hope that helps!