Science has propelled humanity forward, unlocking mysteries and improving lives. Yet, history is littered with moments when scientific knowledge was twisted or misapplied, leading to devastating consequences. From well-intentioned inventions gone awry to calculated cruelty masked as research, the misuse of science has left deep scars on society. Understanding these notorious cases reminds us that ambition, ignorance, and malice can turn discovery into disaster. Let’s explore 15 of history’s most catastrophic scientific missteps—and the cautionary tales they offer for the future.