Was Thomas Midgley Jr. the biggest killer of the 20th century?

I asked a question b4 about Vasili Arkhipov who was one of the biggest heroes of the 20th century yet not many people seemed to know he was, he prevented nuclear war by voting no to firing nuclear weapons while on a sub during the Cuban missile crisis. The world would be a very different place if he had voted differently.
I decided to continue on with an "accidental asshole." Thomas Midgley Jr. invented CFCs and tetraethyl lead.