When I finally make it as a filmmaker, I'll have an ironclad rule: tell my story in a trilogy and get the hell out. This applies to all my reboots as well as anything else I make (with the exception of Saga of the Universe Runner, but the nature of that tale necessitates a longer series). With that in mind, I present the final chapter of my Transformers reboot: The Wrath of Unicron.
The film opens with Starscream's Decepticons approaching the coordinates of Cybertron, which they gained from Omega Supreme during his time in their ranks. Starscream has maneuvered Soundwave into the position of Decepticon leader, with Starscream pulling the strings from a safe position. Lazerbeak and Buzzsaw ask Starscream why he doesn't just take the leadership position for himself; Starscream responds that he doesn't know for sure if Megatron is dead, and if the former Decepticon leader is still alive, Starscream wants to ensure Megatron's wrath comes down on someone other than himself. Soundwave isn't just a puppet, he's a decoy.
When the Decepticons reach the coordinates, they are shocked to find a giant machine planet where they expected nothing but debris. Thousands of vicious Transformers stream from the planet and take the Decepticons prisoner. The Decepticons are brought to the planet's core, where a gigantic face introduces himself as Unicron. He demands to know what the Decepticons want; Starscream urges Soundwave to tell Unicron that the Decepticons were driven from their world by the "evil Autobots."
Unicron is less interested in the war between Autobots and Decepticons than he is in a world full of organic life. He orders his servants, which he calls Predacons, to travel to the planet and destroy the Autobots before his arrival; afterward he will devour the planet and use its energy as sustenance. Unicron orders the leader of the Predacons, Razorclaw, to eliminate the Decepticons. The Decepticons — including Soundwave, Lazerbeak, Buzzsaw, and Shockwave — are obliterated by the Predacons, while Starscream flees for his life, the only survivor. Starscream runs back to Earth, the only inhabited world he knows, with the Predacons and Unicron in pursuit.
On Earth, Megatron, having been rebuilt by Omega Supreme, is on trial for crimes against humanity. In a converted basketball stadium, Megatron is forced to hear the testimonies by various Autobots and humans — most of whom are the families and friends of those who were killed at the Autobot Conference Massacre and the Battle of Camp Hero. Also testifying is Carly Miller, who was crippled in the Battle of Camp Hero to the point of needing her left arm and leg amputated and replaced with bionic limbs. While Carly's limbs are superior to her old ones in every way, Carly is afflicted with a severe case of PTSD. Far from her once-exuberant self, she is now withdrawn and filled with hatred for the Decepticons, especially Megatron. Wheeljack, Carly's best Autobot friend, tries to cheer his friend up, to no avail.
Megatron refuses to apologize for his actions; he argues that humanity was sick and dying, and needed his iron fist to turn it away from the path of self-destruction. This causes the stadium to erupt into chaos; only Optimus Prime's calming voice quiets the crowd. Optimus tells the gathered humans and Autobots that Megatron's crimes were monstrous, but that the Decepticon needs compassion and guidance, not vengeance. Optimus still believes his brother can be redeemed, but the Autobot-human jury do not see it that way. Megatron is found guilty for his crimes and sentenced to death. Optimus begins to protest, but Elita Prime and the rest of their inner circle — the rebuilt Ironhide, Grimlock, Wheeljack, Bumblebee, Omega Supreme, Jazz, Arcee, Hot Rod, and Carly — tell Optimus that Megatron was found guilty within the confines of human and Autobot law. Would Optimus become a criminal just to save his brother, a mass murderer?
Optimus is about to answer when Starscream bursts through the roof of the stadium, screaming "They are here!!!" Explosions then rock the stadium. The Autobots rush out of the stadium, seeing thousands of Predacons descend on the city. Omega Supreme blasts hundreds of the Predacons apart, but Razorclaw joins with several of his minions to create a massive Predacon amalgam. The two behemoths pummel each other in a brutal battle until the Predaking decapitates Omega. The Autobots, enraged by the death of their friend, furiously engage the Predacons.
The battle is a rout. Bumblebee is crushed into pieces by the Predaking. Jazz is crippled by a Predacon legion. Arcee is destroyed trying to evacuate humans from the city. Grimlock is sliced apart by Predacon particle beams. Carly tries to help her friends, destroying many Predacons with her transforming arm cannon, but the battle is simply unwinnable.
Then, just before the last of the heroes are killed, a great roar echoes through the city. Optimus Prime, conspicuously absent during the battle, arrives with every Autobot in the city, and more Autobots stream in from around the world. As the Autobot horde slams into the Predacon forces, Optimus explains to his friends that he was calling for reinforcements. Optimus sees the bodies of his fallen comrades and tells the survivors that their deaths will not be in vain.
As the Autobots fight for the very future of robot and human, Starscream frees Megatron and urges a hasty exit. But Megatron has not forgotten Starscream's betrayal. The former Decepticon leader plunges his hand into Starscream's chest and pulls out the coward's reactor, crushing it in his hand. Starscream falls to the ground, face locked in a silent howl of agony.
Megatron walks out of the stadium to see his brother and the Autobots fighting valiantly against the Predacons. He witnesses humans fighting alongside Autobots, sacrificing their lives to protect their robot friends. Seeing humans giving their lives to protect his people changes Megatron. He realizes that humanity is not a lost cause after all, and charges into battle against the Predacons at his brother's side.
The Autobots and humans are shocked to see Megatron fighting at their side, but Optimus is galvanizes by his brother's presence. The two brothers spearhead an assault against the Predacon lines, and eventually break them. As the Autobots and humans mop up the Predacon forces, a shadow falls over the city.
The citizens of Earth look up to see Unicron in the sky, ready to devour Earth. For the first time, Optimus and Elita have no idea what to do. Even Megatron is stymied, until he remembers what he did to Starscream. Megatron tells Optimus that if Unicron is really a machine, then it must have a reactor. All they have to do is destroy the reactor, or at the very least disable it until they figure out a way to get Unicron to a safe distance away from Earth.
As Optimus and Megatron prepare to head up to Unicron, a blast of energy suddenly heads for Carly. Optimus throws himself between Carly and the blast; the energy tears through his torso. Megatron and Carly turn to see Razorclaw feebly aiming a glowing blaster rifle before falling lifelessly to the ground. Megatron cradles Optimus in his arms; Optimus asks Megatron not to let his death be in vain, asks Megatron to save humanity. Megatron tearfully vows that he will. Optimus says "Thank you...Pax," and dies. Tears stream down Carly's cheeks as she whispers her gratitude to Optimus, while Megatron stumbles to his feet in despair.
Elita Prime and the other Autobots are beside themselves with grief, but Megatron chokes out words of comfort, telling them to be strong. He asks Elita and the Autobots to distract Unicron while he finds a way inside the giant machine. Elita reluctantly agrees, though she still despises Megatron. The Autobots — with Carly leading a secondary wave of assault ships — and Megatron fly up to Unicron, who transforms into a mammoth robot. The Autobots and Carly's armada fight Unicron, who is more amused than threatened.
While the Autobots and Carly distract Unicron, Megatron finds a way inside. He tears his way through Unicron's internal defenses, until he finally arrives at the monster's reactor. It is there that Megatron discovers the horrible truth. Playing over and over again on the walls encircling the reactor are images of Unicron's past. There are images of organics roaming free on Unicron's surface, creating machine servants, the slaves revolting, the free robots turning the planet into a giant sentient machine, then the robots destroying themselves and their world through a brutal war. Megatron watches as the remnants of the planet slowly bring themselves back together over millions of years, millions of years of agony in which the consciousness of the planet went mad with grief and pain. The planet, no longer a world of peace called Cybertron, renames itself Unicron. While Megatron is moved by the terrible truth about Unicron, he knows that Earth must be saved. Megatron attempts to disable the reactor, but his weapons are not powerful enough. Megatron finally realizes that he has to sacrifice himself to destroy the reactor. By self-destructing, he will create an explosion powerful enough to destroy the reactor. Megatron smiles to himself, saying that he will see his brother soon, and flies into the reactor, detonating himself as he slams into it.
Megatron's sacrifice is successful; the reactor implodes, ripping apart Unicron's insides and reducing the giant robot to a lifeless husk. Elita Prime and the Autobots realize what Megatron has done, and are speechless. Weeks later, Elita Prime and the Autobots preside over the unveiling of a statue of Optimus Prime in honor of his sacrifice. And though Megatron does not get a statue in light of his crimes, at the base of Optimus's statue is a painting of Megatron with a plaque detailing his heroic final act. Elita Prime and her Autobot allies are deemed the Guardians of Humanity, and they help their organic friends create the first interstellar starships, in a grand project meant to bring humanity and machines together in lasting friendship. Carly becomes the commander of the first interstellar vessel, which is also a new type of Transformer; a Star-faring Robot, or Starbot.
The galaxy, with all of its mysteries and wonders, awaits.