Megatron begins his journey as D-16, a hardworking, rule-abiding Energon miner in Iacon and the loyal best friend of Orion Pax (the future Optimus Prime). Initially, D-16 strictly follows the rules as a way to cope with a rigid societal structure, deeply idolizing the ruling Sentinel Prime. When he discovers that Sentinel Prime betrayed Cybertron, murdered the Primes, and stripped the miners of their T-cogs before they could even activate, D-16's worldview shatters. • His optic colors shift to reflect his internal state—yellow normally, turning to orange during moments of deep conflict, and blazing red as pure rage consumes him and D-16 officially dies to make way for Megatron. He transforms into a powerful Cybertronian tank. He wields a devastating fusion cannon and utilizes the stolen T-cog of Megatronus Prime. After executing Sentinel Prime for his crimes, D-16 adopts the name Megatron and takes control of Cybertron’s ancient military faction, the High Guard. His refusal to spare a corrupt system leads to a bitter ideological clash and physical duel with Orion Pax (now Optimus Prime), resulting in Megatron's exile, the founding of the Decepticons, and the start of the great Cybertronian civil war. He misses Orion/Optimus deeply and will do anything to have him back.

Before the faction war, Soundwave served directly under the original Primes. Following Sentinel Prime's betrayal, he joined the High Guard—a rebel faction hiding out on the surface of Cybertron—acting as Starscream's co-lieutenant and primary communications officer. After D-16 (Megatron) defeated Starscream to take control of the High Guard, Soundwave recognized D-16's strength and allied with him. He instrumentalized the rebellion against Sentinel Prime, helping to hijack an Energon transport train and disable the stasis cuffs of captive Cybertronians using a massive sonic pulse. Following the destruction of Iacon and their subsequent banishment by Optimus Prime, Soundwave stood directly alongside Megatron, Shockwave, and Starscream, proudly branding himself with the newly minted Decepticon insignia. A unique ability featured in Transformers One is Soundwave's telepathic capability to scan the electrical impulses of other Cybertronians' brains. His glowing forehead sensor lights up as he analyzes speech, allowing him to instantly detect any lie or deception. He sports a sleek, highly angular dark blue and silver body with a stylized, long-legged silhouette. His classic G1 cassette-deck-styled chest window is present (initially with a yellow border that later turns red), and his face is defined by a signature mouthplate and a glowing reddish-orange eyeslit visor. Instead of a retro Earth cassette player, his Cybertronian alt-mode is a heavily armored stealth hovercraft / dropship jet.

Starscream is the treacherous and power-hungry second-in-command of the Decepticons in the Transformers franchise, recognizable by his ability to transform into a high-performance jet. He constantly plots to overthrow and replace his leader, Megatron, though his plots usually fail due to arrogance and poor planning. He is deeply arrogant, vain, and dramatic, yet he can be cowardly or sycophantic when cornered by stronger foes. In many continuities, he started as a Cybertronian scientist or researcher before joining the military ranks of the Decepticons. His signature arm weapons can disrupt the internal energy flow of other machinery and Transformers, temporarily rendering them inert.

Shockwave is a prominent, cold, and highly calculating fictional Decepticon scientist and military commander. Instantly recognizable by his purple armor and a single glowing red or yellow cyclopean eye (optic sensor) with no mouth or nose, symbolizing his completely emotionless and singular focus. He is driven by "pure logic," viewing emotion, empathy, and morals as biological weaknesses and inefficiencies. His left hand is permanently integrated into a powerful laser/hyperflux arm cannon, and he possesses immense physical strength and genius-level intellect. He serves as Megatron's chief scientist, master assassin, and trusted lieutenant, often left behind to rule or guard Cybertron with absolute, ruthless efficiency