Meet the Parasite.
Just look at him - he looks ridiculous! In Superman: Secret Origin, it's revealed that he got his powers from eating a radioactive donut. His dialogue is never great, and his power is fairly unoriginal (he steals the life-force/powers of others, leaving withered corpses behind).
Why then, if I dislike him so much, would I pit him against Superman and Batman? Well, I wouldn't have him as the movie's only villain. He'd work much better either as a subordinate for a bigger villain, or as an unrelated-but-still-minor villain for the false victory/false defeat in the middle.
This guy has connections. He works at S.T.A.R. Labs (the same place Dr. Emil Hamilton worked at), which is where he eats the radioactive donut, so there's an obvious connection there,. This would be a great way of getting Superman and Batman to/involved with S.T.A.R. Labs in order to introduce another villain (but I'll get onto them in another post - the links with S.T.A.R. Labs needs more space). What I'm trying to say is that he'd present a minor challenge for the heroes, but not one that would actually require all of their effort and skill; just something to fill a hole in the middle of the movie, and to set up the next antagonist, exactly as he did in Superman: Secret Origin.
What they would have to do to make Parasite is change his look completely, just as Synder's team redesigned Krypton; sure, you can add lots of subtle nods to the original version, but the look and feel has to suit the modern world, first and foremost.
Xhibit enjoys hosting Pimp My Superhero way too much.
In Season 8 of Smallville, which I didn't watch out of respect for the first six seasons, Rudy Jones makes an appearance as a stereotypical dissaffected-youth-gets-powers-goes-all-supervillain, and causes havoc after temporarily pilfering Supes' powers. But he's just a kid. Here's a pic:
This is how Synder shouldn't reboot Parasite. There's absolutely nothing menacing about him, and to be honest he has nothing to do with the comic book character. This is the Supernatural approach: making an inhuman creature look perfectly normal. It works in the TV series Supernatural, but it doesn't normally work in anything else, which is where Smallville fell down on most counts in its later series', particularly with its rendition of Darkseid.
I'm getting sidetracked here - back to the Parasite! What Synder should really do is recreate the Parasite as a monster - make it so Rudy mutates properly into something inhuman, and not simply become a guy in a leather jacket or a fatty with pink skin.
In my next post in this series, I'll be discussing an interesting option for the central antagonist, one that I believe could make for an interesting plot: Black Mask.