2. Eradicator
Eradicator was originally a piece of Kryptonian technology, containing information about the planet, which was sent in to space with the intention of preserving the culture of Krypton. It gained sentience and began to carry out this 'preservation' via the method of eradicating all other cultures and terraforming their planets to resemble Krypton. We've just seen Kryptonian terraforming apparatus in
Man of Steel, so the appearance of Eradicator would be a very easily explainable thing. Imagine, if you will, that sentient remnants of the destroyed world engine are being examined by Earth's scientists, in order for our planet to learn from the advanced otherworldly technology. One of the remnants attaches itself to one of the scientists and turns him in to the Eradicator - a human imbued with the strength, durability, speed and intelligence of advanced Kryptonian tech, giving him the physical ability to rival Superman in combat. The Eradicator could then continue where Zod left off and attempt to turn Earth in to Krypton through terraforming. It could be an interesting interpretation of the character and one that would fit nicely in to the
Man of Steel universe.