Who was the vampire?

Nothing about this film is stupid. I can only imagine what kind of crap you consider "good," to make a statement like that about this movie.

"IMdB; where 14 year olds can act like jaded 40 year old critics...'

Nobody is the vampire in the film. Unless if you read the book it tells you who the actual vampire is.

The description on imdb is actually lifted from the BOOK's description. To clarify, the book is a series of loosely connected short stories. The film includes all but one of them: the story about a vampire who accidentally sucks the blood of a heroin junkie and starts tripping balls. If I remember correctly, it was in the original script for the film, but apparently it was too tonally different from the other stories. I think the vampire was cast already as well. The original cut of this film was 2.5 hours I think, and it's too bad this flew under the radar and was so critically panned. I'd love to see an extended version!

The vampire was Brandon Routh. The plot was dropped before any filming according to the commentary.

We’re trying to pretend as if these comic books don’t exist. - David Goyer on the DCEU

It was the guy who visited Brad Renfro's character after Jack leaves. He pins him to a wall and threatens him.

The rest of his scenes were cut tho.