That’s a favorite. They were a text book study in how enemies could form alliances when it suited their purposes, but there could never be a “kumbaya” moment between the Narn and Centauri, the interplay was magnificent.
Those moments of interaction could be brilliant, like when Londo brought his former friend Riva to the caves to be murdered by the Narn in order to secure their aid in matters. Or G’Kar’s “dead, dead, dead” chant as he dripped blood, in response to Londo’s nephew trying to apologize for the recently dead.
The psychology was marvelous. I liked the way they explored religion, as well. Everyone has religious beliefs; sometimes they can be harmonized, and sometimes they can’t. It made much more sense than the “Star Trek” idea that religion would disappear because technology.