The Transcendent One
See: Homucifer/Homusatan.
The Transcendent One (TTO) refers to the incarnation of Homura Akemi that took it upon themselves to literally transcend. They are the true antagonist of the work, manipulating everything behind the scenes, including Pinky.
Very little is know about TTO, except that they are disgusted by the current incarnation (Murderface/Chiaki Matsuda), and they attempted to kill Pinky (Corrupted Madokami) in the past, which was implied to have been out of preventing more suffering, although this has yet to have been proven.
She is also implied to lead an organisation (a possible counter-cult to the Blessed Lady Church/Church of the Golden Land) with members named after the Latin Seven Deadly Sins, who have an ambiguous relationship to the story that has yet to be revealed.