Writers 
Humans are inherently both evil and good. They always have been. Each person has a different mix of good and evil. We are all tempted by greed, lust, power, etc. It is up to each of us to resist that temptation or not. Evil is defined as selfishly harming others to one’s benefit. Hoarding wealth while others starve is an example. Torturing and killing others simply for one’s personal amusement is considered the worst form of this because most people can’t understand it. Most people understand well the temptation to harm others if you can gain power and wealth. A certain amount is justified because most want power and wealth and most admire those that acheive it and will help those that have it in order to get some of it too.
We are born with a conscience feelings of pride or guilt to tell us right from wrong, but it only advises us, it doesn’t direct or order what we do. The reality for most people is that if they are confident they can do bad things and get away with it, they will do it, relative to the limits of their conscience. And that conscience must be shaped and developed during childhood. Children can be taught to embrace or ignore their conscience. Thus, it is critical for a society that its people believe that there is justice, that they will be caught and held accountable if they are bad.
These beliefs will teach their children. Unfortunately, culture is ever changing and can easily move toward giving more weight to wealth and power than morality. Indeed, we evolved to put wealth and power first. At the same time, we evolved as small tribes too, and the most successful tribes had unity and internal morality and ethics. A team of individuals all working toward the good of the tribe and helping others in the tribe was ultimately more powerful and wealthy as a tribe than other tribes where infighting and lack of cohesion reigned.
Civilization "the tribal organization and rules of conduct and organization" works to keep us from being evil, if our evolved conscience isn’t enough. At one end, there is the small family tribe where you can’t get away with much before the others beat the snot out of you, or worse, kick you out to die in the wild. That is how humans spent most of our evolution, in small family tribes. Justice was swift. If the biggest and strongest ruled with fear and might to hurt others, the others often banded together to defeat them. However, really smart evil leaders bribe other big strong people to protect their power, giving them a share of the hoarded wealth and power. That is corruption. That is how evil kingdoms are made and this shapes the culture as people follow what seems to work for their leaders. Eventually, they will collapse. Good leaders crush corruption around them instead of encouraging it. However, good leaders are rare. Power corrupts and absolute power corrupts absolutely. Corrupt leaders extend their power and wealth by extending corruption through their society.
Large civilizations, those that were successful enough to become very large, usually have strong systems of laws that ensure the people work together for the common good and those that selfishly follow their own greed instead are punished. But in some ways, they can be evil too for two reasons. One, individual welfare and happiness may be ignored or sacrificed in exchange for forced compliance. A military or police state under a brutal dictator is a successful strategy to make a nation strong, as long as rebels can be kept in check. Justice and punishment can be brutal and swift, ensuring unity and security if not happiness. Another problem with large civilizations, even those which follow good morality, is that it is easier for evil deeds to be committed and the bad people to get away with it, simply because there are too many people, too many to keep track of everyone and their actions. This is where religion comes in, to convince people that you will be punished even after death. Death is no escape from justice, even if civilizational laws and tracking or corruption let you get away with evil deeds. Religion is a very useful tool to ensure compliance from citizens in a large civilization. The best religions are those in which the rules align well with individual conscience. You are not only taught that following the rules is mandatory, but the rules also “feel” right in your heart. Again, conscience is shaped by culture during childhood, so killing foreigners or those of another religion may “feel” good and right by those raised in such a civilization.
Eventually, with science, organization, and detailed laws, you don’t need religion so much because you have technology to catch people. Police and investigators and cameras and CSI tighten the net and make up for the large size of a civilization. Everyone and their actions can be tracked and accounted for, regardless of the sheer numbers. Justice will catch up to you eventually in life. There is nowhere to hide, no secrets or privacy. This technology can be viewed positively or negatively depending on what type of civilization you have, such as “Big Brother” of “1984” dictatorship. The technology itself isn’t good or evil, it’s how and by whom and for what purpose it is used.
However, when civilization’s technology, the lack of privacy and the intensity and effectiveness of the police become very strong to the point where people lack adequate freedom, then people rebel. The outlaw, the criminal becomes the hero. And even in the best and most moral societies, humans resent being forced in a cage of laws too tightly, regardless of the security.
Culture is also a very important part of a civilization, to teach our young the importance of being good, that it isn’t just a matter of being caught and punished for being bad, but also, that other people will respect you and praise you and you will have high status and everyone wants to be around you, simply because you are good, a hero. This feeds your conscience, making it very effective at self-control. That is more important than basic religion because it is internalized. Indeed, the most effective religions are those that focus on being good simply to be good, rather than being stoned or sent to hell for being bad. Also, the big problem with religions is that they often teach people to use them as excuses to commit evil against people who worship other religions. In that way, they don’t bolster our consciences; they are used as excuses to ignore our conscience, our morality.