1. Unicron
Hasbro/TakaraI mean, seriously, who else was it going to be? In all forms of media that the planet-devouring Unicron has appeared in, hes presented as the ultimate foe, the Devil-like entity in which the Autobots and Decepticons must join forces with to destroy or become slaves to him. As both a character in himself and a catalyst for other characters to emerge, Unicron can be seen as a bonder of Transformers. They flock to either fight against him or join with him, and every battle fought against the planet Transformer is seen as an apocalyptic battle, one that brings every type of Transformer together from across the universe. Additionally, unlike many other duos Ive listed here, you dont always need a Primus to have a Unicron. Despite much of the Transformers fandom being rather bored to death of apocalyptic, penultimate story climaxes involving Unicron and/or Primus, having a Unicron in the live-action films could result in a literally galaxy-spanning piece of film-making, regardless of context (because, you know, thats never really stopped Bay so far).
Did you agree with this list? Or are there other giant Transformers you'd love to see? Let us know in the comments section below!