EXCLUDING UNICRON and PRIMUS who is the most powerful transformer?
If Primus and Unicron are not allowed, the next one that comes to mind is Metroplex.
EDIT: Also, are any kinds of power-ups or anything of the sort allowed? If so, then certain versions of characters like Galvatron and Optimus would be up there as well.
@MrDirector786: Yea, I'll allow power-ups. Is there any kind of power ranking/list?
I don't know if there's any ranking or list anywhere.
If power-ups count, then Galvatron from (that piece of crap show) Transformers: Cybertron at the end obtained the omega lock and 4 cyber planet keys, making him more powerful than even Primus (albeit, Primus wasn't exactly at full power because those objects Galvatron had contain Primus' power). He was able to manipulate the black hole left by Unicron's destruction.... yet he also got beaten by Optimus, Scourge, Override, Metroplex, and Evac combined... then again he didn't seem to really be using the power he had much at all otherwise he should have devastated them given what he was doing with all that power.
There was also the massively powered up versions of Optimus and Galvatron from (that even worse show) Transformers: Energon near the end of the series. I believe at one point, Primus powered Optimus up enough that he was actually able to take on Unicron by himself (well, he was also combined with Omega Supreme, but it was mostly Primus' power that enabled him to fight him alone).
if Unicron and Primus aren't allowed then it would shift down to one of the original 13 Primes
- Prima, the first Matrix-Bearer and the first Cybertronian Transformer; leader of the Thirteen. Warrior of Light, he wielded the Star Saber with the Matrix of Leadership as its hilt.
- Megatronus Prime, later known as "The Fallen" as a Herald of Unicron, the guardian of entropy and Warrior of Darkness.
- Vector Prime, the guardian of time and space.
- Nexus Prime (also known as Nexus Maximus), the guardian of Rarefied Energon, capable of splitting into five smaller Transformers thanks to Alpha Trion and Vector Prime, to hide the shards of Prima's sword:
- Solus Prime, the archetype of all Female Transformers - weaponsmith for the Thirteen.
- The Liege Maximo
Note: The Liege Maximo was confirmed in Simon Furman's Alignment story as one of the Thirteen, but that story was "unofficial" and of debatable canonicity. The Liege Maximo was later canonized as one of the Thirteen at 2010's BotCon.
if you're saying anything other than the Thirteen Primes then you really need to read some of the older Transformer books....Unicron and Primus were like the gods of Transformers...the Thirteen Primes are like demigods to the Transformers...all are multiversal entities meaning that there is only one of each of them for all of the multiverse and are capable of reality warping on a minor scale
I almost forgot to mention Thunderwing. In IDW's continuity, he pretty much wiped out Cybertron by himself and the Autobots and Decepticons combined couldn't stop him. He was only stopped because the planet itself opened up and swallowed him whole. And when Thunderwing was resurrected by Bludgeon, the Autobots only beat him by taking advantage of a flaw in his power source - he was resurrected by a power source called ultra-energon but ultra-energon had some kind of flaw that's kind of hard to describe.