I hope this is the right place to pose this question. It is a social question I think.
How does a dictator get others to kill for them. Gaddafi has not to my knowledge killed anyone but he has managed to get others to kill and torture their own people and with great brutality. Hitler did it too and Stalin. How is this and why is this. Are there so many psychopaths around naturally who welcome the opportunity to indulge their proclivities?

Those who are complicit enjoy the rewards and a change of heart usually is fatal.

In Gaddafi's case I think there is a lot of tribalism involved as well.

I hope I’m not necro-threading . Excuse me if I do.

You more or less give the answer away yourself. People can’t easily kill members of the in-group without great reluctance and psychological damage anyway. The trick is to dehumanize the targeted group first, stigmatizing it.

Luckily for the dictators in this world, they often manage to seize power in a already turbulent atmosphere where groups of people are strongly opposed to each other. The dictator then reigns by terror and grants privileges to a minority while stigmatizing and dehumanizing the rest even further. By the rule of fear people have a strong incentive to cooperate with the ruling elite and take part in the reign of terror set out by the dictator.