Antagonist
Character Role Analysis
Hugo Reiss, Kreuz vom Meere
Hugo Reiss is the German consul in San Francisco, while Kreuz vom Meere is the head of the German secret police in San Francisco. But they share the same goal of stopping Baynes from meeting with General Tedeki, sort of. They may be on the same side but they don't exactly get along.
Joe Cinnadella
For most of the book, Cinnadella doesn't seem like an antagonist. Juliana wants to change her life and Joe helps her. So we would call him a companion or romantic interest—except his real goal here is totally opposed to Juliana's. He wants to kill Hawthorne Abendsen, whereas she wants to learn from him.
Wyndham-Matson
All the other antagonists here are evil Nazis (well, Hugo Reiss is more of bumbling Nazi), so why are we lumping Wyndham-Matson in with them? Clearly old W-M isn't that bad a guy; he's just a businessman who looks out for his own interest. But that interest does put him in opposition to Frank Frink and Ed McCarthy, which is the standard definition of an antagonist: dude who opposes the protagonist (even if the opposition isn't mean).