What is malevolence? On the nature, measurement, and distribution of dark traits

Thanks, I mostly agree.

But even in colonialism, individual traits played a role. For example, compare King Leopold II's rule over the Congo Free State vs. other colonial regimes. 

While all colonialism was exploitative, under Leopold's personal rule the Congo saw extraordinarily brutal policies, e.g., his rubber quota system led soldiers to torture and cut off the hands of workers, including children, who failed to meet quotas. Under his rule,1.5-15 million Congolese people died—the total population was only around 15 to 20 million. The brutality was so extreme that it caused public outrage which led other colonial powers to intervene until the Belgian government took control over the Congo Free State from Leopold.

Compare this to, say, British colonial administration during certain periods which, while still overall morally reprehensible, saw much less barbaric policies under some administrators who showed basic compassion for indigenous people. For instance, Governor William Bentinck in India abolished practices like sati (widows burning themselves alive) and implemented other humanitarian reforms. 

One can easily find other examples (e.g. sadistic slave owners vs. more compassionate slave owners). 

In conclusion, I totally agree that power imbalances enabled systemic exploitation regardless of individual temperament. But individual traits significantly affected how much suffering and death that exploitation created in practice.^[1] 

1. ^{^}

   Also, slavery and colonialism were ultimately abolished (in the Western world). My guess is that those who advocated for these reforms were, on average, more compassionate and less malevolent than those who tried to preserve these practices. Of course, the reformers were also heavily influenced by great ideas like the Enlightenment / classic liberalism. 

I don't have enough data about it, but I think it is possible that these horrible mass behaviors start by some dark individuals doing it first... and others gradually joining them after observing that the behavior wasn't punished, and maybe that they kinda need to do the same thing in order to remain competitive.

In other words, the average person is quite happy to join some evil behavior that is socially approved, but there are individuals who are quite happy to initiate it. Removing those individuals from the positions of power could stop many such avalanches.

(In my model, the average person is kinda amoral -- happy to copy most behaviors of their neighbors, good and bad alike -- and then we have small fractions of genuinely good and genuinely bad people, who act outside the Overton window; plus we can make the society better or worse by incentives and propaganda. For example, punishing bad behavior will deter most people, and stories about heroes will inspire some.)

EDIT:

For example, you mention colonialism. Maybe most people approved of it, but only some of them made the decisions and organized it. Remove the organizers, and there is no colonialism. More importantly, I think that most people approved of having the colonies simply because it was the status quo. The average person's moral compass could probably be best described as "don't do weird things".