Evil has many connotations attached to it such as murder, death, hurt, harshness, crime, cruelty, slavery, ect. Based on many of the connotations, evil would be more of an act. But that leads us to a question--how do such things form in us? Is it exclusive to the human race, or is it an occurance in all species? At this moment, I am gonna have to say that evil is something that is related to humans.
The Female Black Widow kills/eats the male after mating. This is something that happens in nature. Is it evil that the female does this, probably not. It is something that instinctual. But then, why would it be any different with humans? Evil could
be considered as a human characteristic. The laws that humans have set up fight evils, such as rape, murder, theft. To many questions...
I personally think that it is more of a "cultural catch-all" as you said. Obviously other species don't recognize evil, that I am aware of. Unless, you have any to say that will change my mind, then that is what I am gonna have to stay with for now.