Fritz Haber, the Veritasium video about him is fascinating (The Man who Killed Milioms and Saved Bilions). He developed the chemical process to efficiently synthesize ammonia, one of the key discoveries that allowed mass adoption of fertilizers and the incredibly rapid growth of the human population in the 20th century (you could say that thanks to him, bilions of people could live and be fed by modern agriculture).
Tragically, he also had a fundamental role in developing chemical weapons during WWI, although he belived their use would reduce the number of deaths as army would simply avoid gassed zones, so who knows if he really intended and believed in the milions of deaths he caused. Ironically, he also helped developing Zyklon B during the rise of nazism (while it was still used as a pesticide), but was quickly forced to flee from Germany because of jewish origin. Later, his last invention would be used to kill even more people.
Fritz Haber, the Veritasium video about him is fascinating (The Man who Killed Milioms and Saved Bilions). He developed the chemical process to efficiently synthesize ammonia, one of the key discoveries that allowed mass adoption of fertilizers and the incredibly rapid growth of the human population in the 20th century (you could say that thanks to him, bilions of people could live and be fed by modern agriculture).
Tragically, he also had a fundamental role in developing chemical weapons during WWI, although he belived their use would reduce the number of deaths as army would simply avoid gassed zones, so who knows if he really intended and believed in the milions of deaths he caused. Ironically, he also helped developing Zyklon B during the rise of nazism (while it was still used as a pesticide), but was quickly forced to flee from Germany because of jewish origin. Later, his last invention would be used to kill even more people.