Black Superman or not, Brixton wasn't working alone in his attempts to wipe out a good portion of humanity with the Snowflake virus. He is an operative of the techno-terrorist organization Eteon, working, as the finale reveals, under the orders of its mysterious Director.
The Director of Eteon is heard but not seen at the end Hobbs & Shaw, ordering Brixton's termination via long-distance Control-Alt-Delete and then telling Hobbs the pair know each other, and will be seeing each other soon. Reducing the master villain to a disembodied voice wasn't always the plan: Dwayne Johnson told Screen Rant that the production had originally tried to cast Hobbs & Shaw director David Leitch's John Wick star Keanu Reeves, but that it was decided to leave his identity a mystery for the time being. His heavily-modulated voice was supplied by Ryan Reynolds, under his pseudonym "Champ Nightingale."
Reynolds also figures in the film's other big loose end, in a post-credit scene where his CIA agent Victor Locke makes a call to Hobbs laying out the discovery of a new super-virus before realizing he's explained all the horrid details to Hobbs' daughter, Sam (Eliana Su'a). The scene is mostly an extended Deadpool-style Reynolds riff, which means it's probably not binding for the sequel. The same is likely true with the fact that Reynolds plays both a good and a bad guy in the film's finale, though now at least the potential seed is planted for Locke to wind up being the big bad.
Whoever it is, it may take more than one sequel to find out. In theory, Eteon could have as many nesting super-agents as there are big-name actors willing to fight Johnson and Statham.
