I'm hoping that the identity of Mr. Oz isn't what it currently appears to be (don't want to include spoilers). The greatest part of Superman's backstory is the altruistic nature of his birth parents. I don't like what this means for that character. Hoping it's not him.
Further, the killing of Metallo removes yet another classic villain from the Superman universe---a trend that befuddled Superman's story arcs since New 52. Metallo never really got a good arc, and he's a character who a writer should be able to build around.
I wish Mr. Oz was Superbly Prime or Ozymandias like most suspected. I'm not liking this.