AMC’s Seven Deadly Sins: Which Was The Deadliest? Or Was There An Eighth?

Today’s Matador CC just begs the question: which was AMC’s Deadliest Sin, that most led to its demise as an independent automaker? Note: I didn’t say “Most Fascinating Sin” (I’m looking at the Matador coupe). To narrow it down we’re talking pre-Renault takeover, but not earlier than say 1965, so the Alliance gets a pass. And maybe you don’t agree with my nominations; so bring on your own.