DS9 was the antithesis of the "breakout character" concept and, as such, didn't have any, IMHO.
DS9 was the only Trek show that was a true ensemble show to the core. Each member of the main cast, as well as a whole host of recurring characters, were well developed, well-rounded characters who played major roles in the stories. There was not a single member of the main cast who didn't regularly have episodes focused on them, and there were even quite a few episodes in which the main cast took a back seat so that we could focus on a story featuring a recurring guest star. (The lone exception to all this I can think of is Jake, who was not nearly as well developed as some of the others, but still got his fair share of attention.)
I don't think there's one or two characters that people think of when they think DS9, the way you think of Kirk and Spock, or Picard and Data, or Seven and the Doctor. I think DS9 was a true ensemble in every sense of the word, and was better for it.