spetznaz
Senior Fanboy Killer
Least: Captain America. Yes, I know how recent adaptations have made Steve many things, but his origin story (if that hasn’t been changed too) was of a good hearted but weak young man striving to make a difference. He decided to serve in the only way he could, but literally offering himself. While recent years have changed many things, his original characterization was as far from evil/villainy as one could get.
Spider-Man: Peter is similar to Steve, just a bit more impulsive. Also a good cat that would require a significant push to make evil. He has faced real reasons and tragedies that would make lesser men turn, but he has still remained largely true.
Superman: This is the one character of the three that has the greatest potential for evil. For one, he is not even human ...he merely looks like one, but is anything but. There is something frightfully deceptive in that. He has powers beyond those of most heroes, and it is easy to see how he can decide to make thins ‘better.’ He could go to space, float about listening to conversations with his super hearing (hey ...if a man can fly a man can ‘hear’ in the vacuum of space), seeing with his super sight, and lobotomize ‘undesirables’ with his heat vision. He has great power, but he was born with it. It was not a sacrifice he made like Steve (sacrifice because the experiment could have gone wrong), and it wasn’t thrust on him through an accident like Peter. He was literally born an ‘ubermensch.’ It is only by fortune and chance that he was found by the Kents. Had the rocket landed in Nazi Germany (or as in Red Son, the Soviet Union, he would have been something totally different).
Lex Luthor is right. Superman is an absolute monster, and just because he has not turned does not mean he will not. It is almost a given. After all, he is a man-child with the powers of a small god....and like a kid with a termitarium, it is only a matter of time before he takes his magnifying glass and decides to crispy-crisp some insects.
Superman, by far, is the most evil thing of the three. He just has not turned ...yet.