An explanation for this; I've gotten a fair number of AU messages detailing a verse where Finn from Adventure Time is a Decepticon and how that would work. I personally heavily dislike this notion; I have never seen any evidence that the Decepticons are anything other than vicious specisist monsters, a full-circle revolution under the command of a sadistic tyrant and a mean-spirited coward. Accordingly, I wrote this to analyze just what would happen if Finn was a Decepticon, and the consequences of it.
Disclaimer: I do not own Transformers or Adventure Time.
Finn the Decepticon walked slowly, his heavy tread shaking the ground.
He winced and trembled as he felt the broken bones of the dead under his feet, tiny organics smaller than his finger. So many of them, they couldn't fit into his head. The numbers were too big, everything was too big.
The smell of an atmosphere set aflame stunk in his nasal receptors. The sight of ten trillion organics driven forth for the Insecticons to devour and grind into pulp to feed the fabricator-engines of the factories they had built here, it was set into his data-tracks.
The ground trembled and sank, and miles behind him a titanic tendril from the Nemesis itself busily sucked out every last bit of mineral resources this planet had to offer. In mere days, the planet would collapse in on itself, and it would be a lifeless pile of rock, all resources and life extinguished forevermore.
Deep in his Spark, a solitary remnant of the protoform he had been whimpered miserably.
"It wasn't supposed to be this way," Finn whispered, over the screams of the dead and dying he couldn't forget. He wouldn't forget, he mustn't forget. He had not done the deed, but he was a Decepticon, and Decepticons had killed them all. He was complicit, and his hands were stained all the same.
He felt as though the grime had been wiped away from optics that had been blinded for too long, and what was before him was so terrible he might wish to be blinded again. But he dared not wish for it. Not now, not again.
Never again, he swore in the deepest reaches of his processor.
In a nano-click, he prayed that Primus strike him down and take his Spark back. He could never take this back, this treachery of a single moment. He imagined walking in the ranks of his fellow Decepticons again, and his fuel tanks twisted at the thought. To walk among mechs and femmes he had called friend, knowing in every corner of his Spark the horror they had visited on a thousand and twenty-two worlds like this one. To finally smell the stink of the Chaos-Bringer's legacy on their oil-stained claws and faces, to know at last that his chosen allies had all done things so evil and terrible that no good sapient in all the multiverse would ever walk with him again, not after the stain of associating with such…
Finn shuddered. He had thought it was for a good cause. He had thought they would do good, that one day the way would be over, and the Autobots would accept defeat and they could return home together.
He wept and cried as he came to terms with the terrible knowledge, that this would never happen. Either the Decepticons would kill the Autobots, or the Decepticons would be put down like mad cyber-dogs.
The magnificent Megatron, brilliant Shockwave, ferocious Strika… all the rank and file of the Decepticons, his friends, his family, Finn himself… the Decepticons were monsters. Finn tried not to cry at the realization.
Finn whimpered as Jake slouched over, downcast and shaking as badly as Finn himself.
Neither of them said anything.
Today, the Decepticons had murdered a world. There was no turning back from this, and they knew it.
"Jake?" Finn said quietly.
"…yeah?" Jake said, his body broad and canine, something of an atavistic callback to the long-extinct Predacons.
Finn needed a moment. "I think… I think we're the bad guys."
Neither of them said anything.
It was a silence thick with mournful agreement.