Inspiration from the current IDW Transformers continuity along with the currently running at this moment IDW Shattered Glass miniseries.
The planet Cybertron the home of the giant robotic transforming species known as the Cybertronians, their society founded by the ambitions of the original 13 Primes which gave birth to the oppressive faction known as the Autobots. Their rule unchallenged and unquestioned as their high elite lived in luxury sipping on the fuel known as Energon while those considered lesser were forced to live in horrible conditions and made to slave away doing the dirty work to building the Autobot controlled lifestyle.
Until a nameless miner had gotten tired and led a revolt along with his fellow miners which led him forced to slave away in the gladiator arena which was there dissenters were sent to die to serve as an example. However this miner became the ultimate champion of the arena and created a faction to protest against the oppressive regime of the Autobots named the Ascenticons. Their peaceful protests were met with violent opposition from the Autobots secret police and were dubbed 'Decepticons'. The miner had adopted the name Megatron from the name Megatronus who was considered to be 'the Fallen', a member of the original 13 Primes until cast out.
Their support and popularity grew growing civil unrest on the streets until Megatron had managed to kill Nova Prime, the leader of the Autobots and the First Senator of Cybertron (basically their leader) which turned this conflict into a full blown war that encompassed the entire of Cybertron.
Countless cycles of this war passed on risk on destroying the planet until the Autobots had found the Ascenticon base and Megatron stayed behind to fight the invading Autobots to give them time to retreat with orders to get off Cybertron and to seek shelter. He was captured and imprisoned made to watch the news of and footage of the war as to torture him further along with the other torture he was subjected to.
Starscream his chosen successor as leader of the Ascenticons, it seemed had found it within to disobey his orders and continued the war against the Autobots. It seemed that it was working as Starscream had masterminded riots at Autobot controlled prisons to release dissenters and captured Ascenticons and they had sent messages and pleas out to Cybertronian colonies for help to take down the Autobots once and for all. It seemed when the news of the war hit the oppressive colonies, riots broke out and the Autobots stationed there lost control and the Autobots back on Cybertron were unable to send aid due to busy having to focus on the war on Cybertron.
The now feed residents of these colonies came to lend their support and assistance.
It now seemed to be the final days of the war; it looked like the Autobots was losing control of their capital city of Iacon.
"Starscream, you found it within yourself to disobey me and I have never been more glad to have been wrong on the right course of action in my existence..." Megatron grinned in his cell inside the Autobots headquarters as coming up along with his guard was the glaring and menacing purple and grey form of Optimus Prime, the leader of the Autobots after the death of Nova Prime. He had been Orion Pax a particularly brutal officer of the Autobots and had tried to bring Nova Prime's dying body to get medical aid before the Matrix (the ultimate symbol of Autobot leadership) transformed him into a Prime.
"Proud of what your Decepticons have wrought onto Cybertron? I had thought that capturing you would be an end to this war once and for all but it seems that a further example would be needed. I shall have you executed live for all of Cybertron to see. This rebellion shall die with you." Optimus said shaking his head as Megatron laughed.
"The Ascenticon cause is bigger than me, you can kill me but you can't kill an idea. As long as there is at least one Bot willing to stand against Autobot tyranny, the Ascenticons cannot be destroyed!" Megatron shot back as Optimus scoffed.
"Big talk from someone who is nothing more than a filthy miner who didn't know his place on Cybertron, you Decepticons brought dangerous talk of 'rights' and 'empathy' and disrupted our order. You even adopted the name of the Fallen." Optimus replied as Megatron shook his head.
"Megatronus was the original Prime who wanted us Cybertronians to live in peace with our fellow beings in the universe, he wanted everyone to live in harmony and equal with no hatred and corruption. The Primes wanted to conquer and he rebelled, the Ascenticons were founded on his philosophy. Your 'order' was subjugating beings you considered less than you and used violence when they didn't fall in line with you fascists." Megatron retorted as Optimus had his guards bring him out.
"I should have been there at your hideout to blast your head off." Optimus said and even as he was being dragged in cuffs Megatron laughed his head off. "You find that amusing?" Optimus asked as Megatron grinned.
"I do indeed; we both you know are too much of a coward to be out on the field anymore." Megatron replied as Optimus was furious as the guards were tense as most Autobots were terrified to even disagree with him in his presence. To insult him directly meant that you should start praying for Primus that he you would be subjected to a quick and painless death. "Orion Pax used to savour in the brutality of his victims but after the Matrix turned you into a Prime, you became relaxed and allowed yourself to conduct your war from the confines of your office. Do you even know how to fight anymore? I have been fighting ever since the gladiator pits and I was right there on teh battlefield, leading my troops to fight for our freedom!"Megatron proudly shouted facing the furious Optimus as he was dragged to an arena and thrown down as there were cameras to show this live in giant holograms for all of Cybertron to see.
There were Autobot soldiers to fight him to the death with grins on their faces along with Grimlock in his roaring dinosaur form, a peaceful diplomat who wanted to hear the Ascenticons out and was subjected to horrible experiments that transformed his alt mode into a monstrous creature. "I have no pleasure in having to fight you Grimlock and I know there is still pieces of the real you inside. Don't need to ask for forgiveness in what you are forced to do as I know that you are a victim in all this." Megatron said facing up Grimlock with no fear and sympathy in his voice which had Grimlock taken aback but then the soldiers attacked with Megatron doing his best to dodge and fight back with his legs.
Grimlock saw Megatron being beaten down and there was a fight within his mind as he managed to use his tail to swat the soldiers away and he caught a spear in his mouth using it to free Megatron from his cuffs. He was able to take the soldiers down to Optimus' fury and with the last of his free will Grimlock swang his tail at Optimus to take him down to the gladiator pit.
Megatron wasted no time in savagely attacking Optimus as he tried to fight back and even broke his faceplate. Optimus managed to use his Prime strength and Megatron not being at full strength due to his torture in captivity to his advantage. Optimus went back feeling weakened and hiding a blaster behind his back said "Wait, please have mercy... We can talk this out..." He then got his blaster out and shot Megatron in the back but he managed to get a punch to the chest knocking the Matrix out from under his chest windows before Optimus was helped up from his soldiers.
Optimus furiously ordered someone to retrieve the Matrix and a recently forged young purple and black soldier by the name of Hot Rod nervously went down to the pit to get at it. Suddenly the intercom went on as the panicked voice of Ultra Magnus said "Optimus sir... the Decepticons led by Starscream have gotten in and we are being overwhelmed..."
Optimus was frantically calling for Magnus to continue as the call got cut off there and then the doors opened and then there was the white and red Starscream coming in with a legion of armed Ascenticons. "Megatron, our great and powerful leader... please forgive me for disobeying your orders as most of us including me I am sorry to say didn't want to give up our home without a fight... I cannot apologise enough to taking so long to try and stage a rescue..."
Megatron sighed as Starscream was especially loyal and near sycophant levels who all but deified him. He remembered when he first met him: Starscream was a peaceful scientist who was keeping outlawed texts and was stormed by Autobot troops. Megatron after he had escaped the gladiator pits along with his fellow gladiators and meeting up with his old fellow miners had came across this attack and had defeated the troops.
Starscream was close to being killed before Megatron took down his assailant, he was in awe and offered them hospitality and they shared his story. He shared his texts including those of Megatronus and that was where he had learned of Megatronus as he listened to Starscream bemoan asking how many are victims of the tyranny of the Autobots: listening to their propaganda, forcing others to do the work needed for their lifestyle to continue and as they go out and conquer other planets under the guise of guiding them. It was Starscream who convinced Megatron that they could band together to make a stand against the Autobots and he could this revolution like he led the miners and gladiators against their oppressors.
Megatron after the Ascenticons was formed always saw himself as more of a warrior than a leader; the best that he could do was give inspiring speeches to keep their Sparks flowing and use the advice of his close allies to carry out war plans.
This along with the fact that the Ascenticons were managing without Megatron better than before made it clear that Starscream was the real leader that the Ascenticons needed.
"The coward Prime asked for mercy when the Autobots have never even thought about mercy! He needed me beaten down and kept captive to even stand a chance and even then he was too scared of fighting me himself! Autocrats living in luxury bringing forth their oppression from the comforts of their bases not wanting to join in the fighting themselves, that is the Autobot way! Freedom for all sentient beings, that is the Ascenticon way!" Megatron shouted to the cameras as the Ascenticons went to work restraining Grimlock down in the pit as well as shooting down Optimus' guard and he ended up falling to the pit after a blast from Starscream. The Ascenticons from around Cybertron having watched this started cheering for Megatron as they could see from the holograms.
Megatron noticed Hot Rod getting the Matrix and it was glowing, no Autobot Primes were being created on his watch! Megatron ran and shoved him aside as he was starting to grow as he ripped the Matrix open and crushed the Spark inside with his hand. There was an explosion and they saw that Megatron was larger and though scarred he was now dark purple with the broken faded pieces of the Matrix down on the floor.
"No!" Optimus shouted in outrage and panic as he got up and charged at Megatron but one punch through the gut ended the spark of Optimus with his corpse falling to the ground.
They all saw that around Cybertron most of the Autobots went on their knees in despair and surrendered; seeing their symbol of the leadership and the Primes destroyed forever ended their resolve as the Ascenticons all started cheering.
Starscream was beside himself with glee as he went up to Megatron saying "it will take some time to get used to but with you leading the Ascenticons we can rebuild Cybertron into what it was always supposed to be..."
"Correction, you will be leading the Starscream. I am resigning and passing leadership onto you. Make sure that the new Cybertron you all build shall be one built on freedom, unity and empathy. Nothing that the Autobots stood for should remain." Megatron interrupted Starscream with him shocked. He turned and put his hand around on his shoulder as he said "I thank you for all the help that you have done but it's now clear to me that I have only ever held you back Starscream. You are what Cybertron and the Ascenticons need."
Megatron then transformed into his cannon and spaceship hybrid alt mode as he flew right through the window of the facility and Starscream went to transform and follow him when he felt the hand of Shockwave stopping him. "The Ascenticons will need to be led and it should be logical to make rebuilding Cybertron and taking care of the Autobots a priority." Shockwave told him as Starscream looked conflicted but then seeing the faces of the Ascenticons faces and the live feed from the holograms made him relent.
"Okay, we should start with rounding up Autobots and tending to our wounded along with burying our dead. We should contact our allies in the colonies and set to work on building a new government. We can plan out on how long it would take to get a new government up and running along with free elections and not the rigged nonsense of the Autobots led Senate..." Starscream said before giving out orders on how to proceed immediately.