Nietzsche: 'good and evil' was invented by the weak to defeat the strong

Nietzsche argued the powerful once simply called their own strength 'good' and weakness 'bad' — no guilt attached. Slave morality, he said, was the underclass's psychological revenge: unable to win by force, they redefined the master's power as 'evil' and their own meekness as virtue. Ordinary morality, on this account, is inverted resentment dressed up as truth.

— Friedrich Nietzsche, On the Genealogy of Morality — First Essay, 1887