Alexander of Alexandria

 was Athanasius' superior, and what Emperor Constantine called "one of the loudest voices" in the debate over the nature of Christ's divinity — a debate eventually settled at the Council of Nicaea in 325. He so regularly sent letters currying Constantine's favour that they essentially backfired. By the time the Council sat, the Emperor simply wished the matter settled, and accused Alexander of simply keeping the arguments going rather than trying to find a way to heal the rift and keep the Roman Empire together. (AUDIO: The Council of Nicaea)

Behind the scenes
Alexander doesn't appear in The Council of Nicaea, but is instead a major offstage presence.