Well, in The Prince, Machiavelli openly addresses the atrocities of mankind, and approaches them honestly and cruelly, for instance, in the book the character creates an enemy he can defeat publicly to earn the respect of others. Put lightly, Machiavelli caused the people of his time, especially those in power, to think about the atrocities of man from a critical standpoint, and thus caused he created a "mirror-for-princes", something through which they could reflect upon their actions with and use metacognition either for deceit and power or good and weakness.