The Wonder Woman teamup continues...
While feeling mysteriously responsible for Medusa, Wonder Woman ranks herself pretty highly; she says "I know of only two, perhaps three, people who could face [the Hydra]," and then says "I can defeat the Hydra."
So, the Hydra can be faced by Wonder Woman, Superman (I'm guessing), or "perhaps"...Martian Manhunter? Shazam (if this is happening after JL 17 or 18)? Zatanna or some other top magician?