Is there such a thing as good and evil if so can man be truly evil or truly good? deities are excluded?

if each side believes the opposition is evil and their cause is just, how can man objectively determine these concepts? in a christian example evil is allowed to exist even though god has the ability to wipe it out. the forces are not equal, in fact ones existence is limited and controlled by the other, thusly making the great universal evil little more than an attack dog to test the faith of men. if that is the case is god all good, if he in fact allows evil to exist though he has direct control over its existence. in my limited understanding i would think a force for good would do all in its power to eliminate evil, it would not keep it around solely to serve its interests. that brings me to my point does evil exist or is what we define as evil simply the undesirable side of human nature, not to say that it cannot be destructive. no bible quotes lest they are supported by a personal argument, please resist the urge to paste. all views are welcome.