Superman- The Cyborg

Out of all the returning Superman, the Cyborg Superman- even more than the Last Son of Krypton- seemed most likely to be the Man of Steel reborn. He looked like Superman, he acted like him. Sure he was damaged, but that was to be expected given what he went through. The storyline really did a great job of building up the Cyborg as Superman reborn. Which made his later betrayal all the more shocking.

In regards to his design, I think it's one of the strongest of the entire Superman mythos. He looks so much like Superman, but dark and twisted. As a villain, he's one of the best- someone with all of Superman's power and more, but without his inherent desire to use them for the benefit of others. All of his power is dedicated to destruction and the annihilation of all life. The Cyborg Superman truly had the potential to be one of Superman's greatest opponents.

So of course the creators chose to nerf him and diminish his power and importance to the point where he's little more than a joke. That's the Superman mythos for ya these days- if you weren't made before 1955, you ain't worth squat!