Few thought that the young woman from East Germany, who Helmut Kohl dismissively called his “girl” in the 1990s, would go far. And yet after 16 years and 16 days Angela Merkel exits the stage just shy of his record as the country’s longest-serving chancellor since World War 2. 

While her former mentor — whom she famously and opportunistically brushed aside — will be forever known as the father of reunification, the scientist who went on to become the nation’s “Mutti” (German for mom) leaves behind a more complicated legacy...