Hmm, well, there's really no debate about it. There's really only one story that has the most astronomically powerful warriors of all time: Alternity.
This story was beyond epic. Possibly the biggest event ever constructed in Transformers fiction. The sheer scale of this story was cosmic, with the whole of reality itself being the set battleground.
Fighting on the side of the Autobots were the Alternity and the Protectors.
The Alternity are higher-dimensional beings having evolved beyond the limits of Cybertronian life. They exist on a higher plane of existence, spanning the entire multiverse, and are contain a collective consciousness that consists of a combination of multiple versions of a single indivdual (i.e. - Alternity Convoy is
every Convoy/Optimus Prime), enabling them to existing in all worlds simultaneously. In order to interact with the physical world, the Alternity make use of material vessels called Auto-Avatars, which resemble the forms of the ordinary lesser being Transformers, but contain characteristics of super-advanced nature of the Alternity (such as being constructed by higher-dimensional material Alternium).
However, as advanced as these Autobots have become, there is a limit to their power: they cannot travel to any times or worlds that existed prior to 2007. This is where the Protectors come in. While not being hyper-dimensional beings like the Alternity, they are elite soldiers who served under the Alternity and are charged with safeguarding timelines. They are able to travel back to times prior to 2003 to confront enemies to time/space who would pose threats at any given time before that year. Also unlike the Alternity, there is only one of each member, rather than each one being every iteration of that character.
To counter this, however, the Deceptcions have their own forces: the Megatron Aggregate and the Questors.
The Megatron Aggregate is the Cons's answer to the Alternity. Having trapped and absorbed the power of the gigantic and intangible "Beast of Time" Hytherion, Megatron had artificially produced his own path to achieving the same hyper-dimensional status of the Alternity. Hytherion is the largest and most fearsome opponent to have ever appeared in Transformers lore (moreso even than Unicron). Because of his cosmically-scaled nature, he is practicall invisible to the physical world of ordinary beings. Knowing this, Megatorn could have easily allowed him to devour time itself, thus eliminating the very origin of existence itself. However, Megs instead chose to take the god-beast's power into himself and forced a psuedo-Alternity metamorphosis upon himself, creating several Auto-Avatars of himself to form the Megatron Aggregate.
Aiding in Megatron's conquest of space-time are the Questors: Starscream, Skywarp, and Thundercracker given new trans-dimensional bodies simialr to, but not as advanced as, those of the Alternity. Still, with their sparks encased in Alternium, they can traverse dimensions and eventually evolve to the higher-dimensional state of existence at which they would be able to combat the Alternity on even ground. The mission of the Questors is to help in the accessing Flatworld, a two-dimensional world that is the home of the Planicrons. The Planicrons are two-dimensional beings who have become the living embodiment of the phrase "'Till All Are One", having become a sophisticated single existence called the Cosmic Driver, which Megatron desires the power of in order to destroy the Alternity.
There has been no other TF fiction as so mind-bogglingly trans-dimensionally scaled as the fiction of the Alternity line.
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