Evil is a question of morality.
Morality is about rules and precepts of social conduct.
As humans evolved to live in groups, rules and codes were formed to protect territory and guarantee safety for members in the group.
So humans were able to work together more efficiently and achieve the success the species enjoys today.
So evil is generally defined as anti-social acts or tendencies.
Acts that harm the society and so indirectly ALL the individuals involved.
Morality as such is not necessary for a person living as a hermit, they do not interact with anyone but nature.
However, whenever people live together, rules are necessary to enable and facilitate social interaction. As societies and cultures vary, so too may morality. It follows that there are as many forms of morality as there are unique groups of people.
While there may be a variance in morality there are many general principles that are agreed upon. These are not limited by religious creed or belief in a particular god.
Numerous religions, belief systems, and philosophies have all come to similar principles and conclusions.
So on one level, there are as many different versions of evil as there are groups of people and on another level, we see many general principles and rules of human respect and conduct.
Is God necessary for morality?
As morality cannot be said to be particular to a specific tradition, creed or group it follows that a particular God is not necessary.
Take for example the golden rule, ‘Treat others as you would be treated’, this rule can be found in many forms and so can be said to be relatively universal. Whilst it is a feature of monotheistic religions and Judaeo-Christianity, it can also be found in Buddhism, Confucianism, Secular Humanism and numerous other belief systems that may not have any specific God or even a God-Idea which deviates radically from traditional western notions.
Moreover the notion of heaven as an incentive to act morally and hell punishment for breaking the moral code, we have the structure and framework for people to practice morality for all the wrong reasons.
Surely the Fear of Hell is no Reason to act Morally
For we are behaving righteously out of coercion and terror of punishment and so not because we want to, but because we HAVE to.
On the other side of the coin, we cannot buy our way into heaven. For if we act righteously expecting a reward then again we are doing it for the WRONG reason.
So the Christian version of God provides no foundation for morality and plenty of room for ‘wrong-headed morality’, morality performed for the ‘wrong’ reasons which are, of course, no morality at all.
Most people have a sense of what is evil, anti-social and undesirable for all naturally, courtesy of evolution and social conditioning.
I think we can all identify evil, ultimately, regardless of tradition or belief.