I believe the guy that invented modern fertilizer saves many, many lives from famine.
I think the same guy worked on or developed the chemicals used in the gas chambers, so….
Fritz Haber. He was Jewish and fled Germany when the Nazi's took over, and his work was used in the gas chambers without his involvement.
That said, that work was the use of chlorine gas as a weapon in world war 1 and he is known today as "The Father of Chemical Warfare" so... yeah.