The vast majority of so-called "justice" or "evil" cases in the world, upon careful analysis, are often tinged with a strong gray area. They are usually intertwined with multiple factors such as conflicting motives, uncertain consequences, incomplete information, historical grievances, cultural backgrounds, and power struggles, making it difficult to categorize them with simple black-and-white labels. However, examples that truly approach "black and white" are indeed extremely rare, and these cases are typically extreme, rare, and almost universally condemned across cultures as "bottom-line" behaviors. They constitute the most fundamental moral red lines of humanity, and once crossed, almost leave no room for defense. What behaviors are closest to the human "moral red line"? 1. Systematic and deliberate destruction of innocents( genocide, causing famine and disease). 2. Extreme exploitation and instrumentalization of the weak( human trafficking, dehumanization). 3. Intentional harm to those with no means of defense( torturing children, humiliating prisoners and civilians, the cruelty of absolute power). Recognizing gray areas does not mean denying the red lines; on the contrary, only by acknowledging that most situations are gray can humanity be more cautious in defending those few truly non-negotiable red lines.