We’ve seen the Killmonger character don his own gold fight suit similar to Black Panther’s and go head-to-head with T’Challa in footage from some action set pieces in the movie.
Bringing Black Panther antagonist, Erik Killmongr to life, took Michael B. Jordan to a “dark place”.
But more than that, the character apparently has some deep emotional and psychological development that Jordan also had to prepare for.
Furthermore, Jordan doesn’t have the African accent that Boseman uses in the movie, which fits with his comic book backstory.