There is no debate about the good Fritz Haber and Carl Bosch did for humanity by inventing the method used to make synthetic fertilizer. It was what they did afterward, during World War I, that is controversial.
Fritz Haber became the director of the Institute for Physical Chemistry that made poisonous chlorine gas. He actively participated in its development and was an advocate for its use, even though poisonous gas was banned by the Hague Conventions of 1899 and 1907. His wife, also a scientist, committed suicide ten days after the first use of chemical warfare. Some believe she did so as a protest. Fritz Haber was the proud recipient of the Iron Cross as an award for his work. Gas warfare killed over 1.3 million people in World War I.
Carl Bosch, working for BASF, a giant German company, converted the ammonia production he helped engineer into munitions production for World War I. Ammonia is the key to fixing nitrogen, the chemical necessary to make either fertilizer or explosives. Bosch took an active part in designing a new plant deep inside Germany that provided Germany with the munitions they needed to stretch out the war.
Both Haber and Bosch were richly rewarded,