Definition of evil

Since you're explaining to us what Jesus said, define "fighting evil". Is it taking up arms against it? Jesus preached peace and everything that comes with it, so if he thought that it was inevitable that evil wins here on earth, then he thought that peace was acquired elsewhere. Is that the sum of those parts? 

If you want to believe that Jesus had a defeatist attitude concerning this, that's your prerogative. I believe that this Jesus character was a bit ahead of his time, and that he preached things that even the most learned scholars of the time couldn't grasp. Funny how something so simple as peace can be such a complicated concept for people.

As for your original question, evil is not having any caring whatsoever of what good does, and acting accordingly. You cannot have a concept of evil without having a concept of good to compare it by. Therefore, a person has to have at least the understanding that good exists, but not care in the least, and actually go out of their way NOT to be good.....in order to be evil.