Wow! Now, that’s a very interesting question. To answer this, let’s begin with the basics. What is evil? Evil is the absence of “good”. But then, what’s good? The absence of evil? Evil is something that can be defined better as “profound immorality.”
As we all know, morality depends on a lot of factors. What’s morally right for you might be morally wrong for someone else and vice versa. This proves that both morality and immorality are mental constructs. I think we all have understood the answer now. “Evil is a mental construct.”
“The fact that man knows right from wrong proves his intellectual superiority to the other creatures; but the fact that he can do wrong proves his moral inferiority to any creatures that cannot.” - Mark Twain
The above quote means that whatever a living creature, apart from human beings does, is neither unethical nor wrong because most of them don’t have a moral code guiding them. Even Susan Neiman in her book Evil in Modern Thought, defined evil as “something that shatters our trust in this world” and trust is guided by moralities. Hence, that proves my point. Feel free to disagree.