In the years immediately prior to WW2, Royal Dutch Shell was a business partner both Internationally and in Germany with IG Farben, the notorious German chemical firm, supplier of Zyklon-B gas to the Nazi death camps.
IG Farben used slave labor.
Extract from Time Magazine article 12 May 1947: Most damning charge was that Farben experimented on slave labor and concentration camp inmates with deadly gases, vaccines and related products. To supply slave labor for its synthetic rubber plant at Oswiecim, Farben allegedly constructed a concentration camp and worked the men, women & children so hard that an estimated 100 a day died from exhaustion. The U.S. would have no trouble proving that the Nazis could not have made war without Farben.