I think it's pretty tight between Starc and Mohammad Amir. Starc won his country the World Cup and Amir won his country the Champions Trophy final. I'd say Starc just edges over Amir right now but with his fragile frame and Amir's County stint, this could very well change.
Not only did Starc win a world cup, he also performed in more than one match (not taking a dig at Amir here, before someone responds with a photo of the CT final scorecard).