This week's Shadowy Villain is the Black Beetle's mysterious compatriot, who we were introduced to in the most recent Booster Gold issue.
We don't have much to go on, other than that they appear to have some dislike for superheroes, since they're having the Black Beetle wipe them out. Based on the last panel they appeared in, I think they may lack hair on the top of their head, but still have some in the back which sort of tufts out, so maybe it's Simon Stagg? Nah, a bit too random.
Actually, my first guess was it was an older Rip Hunter, either disillusioned with the work he's dedicated himself too, or a Rip who, as a more experienced self, is able to perceive this is the proper course of action (or has convinced himself it's the proper course of action). I figured that would explain how they'd know to set that explosive right where Rip started nosing around, but it wouldn't explain why the Shadowy Villain would be confused by Booster Gold being in the Batcave. So scratch Rip.
Hmm, maybe this is the point when Booster finally has to help Brainiac-5 avoid being eaten by a T-Rex, so it could be a Legion foe. Who do they have that time travels? I hope it's not Time Trapper, because the current iteration is Superboy-Prime, and I could go the rest of my life never seeing that character again.