Knock Out is a Decepticon in the Transformers: Prime series. He acts as a Decepticon medic but is also a great warrior. Unlike most Decepticons, not counting the Vehicons drones, he had chosen a car for his vehicle mode. He really enjoys cars and participates in human street racing. The only thing that seems to be his priority is his finish.
Knock Out was called on by Starscream to see if he can repair Megatron. Starscream chastised Knock Out for being late but he explained that it was "a long drive" to which Starscream reacted with distaste towards Knock Out's choice of altmode and wonders why any self-respecting Decepticon would choose a land altmode when he could fly. Knock Out replied that he enjoys how he looks in his current appearance. Starscream then asked if he could repair Megatron. Knock Out said that he was better at "breaking them than fixing them" but agreed to do his best.
Later, Knock Out and Breakdown interfere with the Autobots' museum heist to take the Energon Harvester. He pulled up to Optimus Prime in vehicle mode and wolf whistles at Optimus' altmode. He and Breakdown then engaged the Autobots while Soundwave made off with the Energon Harvester taken from the human children. After Starscream began using the Harvester on Energon deposits, he and Breakdown disabled each other in an attempt to stop Bulkhead from interfering. When they come to the other, Autobots show up to help Bulkhead. Breakdown asked whether they should fight, but Knock Out decided to drive away instead.
When participating in human street race and learned that some Autobot members, namely Bumblebee and Arcee, decided to kidnapped their human partner. Hovever, instead of Jack whom supposedly to be his target, he ended up kidnapped Vincent instead. By using Vincent as hostage, he and Breakdown then corners Autobots, but Optimus Prime, whom unexpectedly came along, is able to save Vince by tearing off Knock Out's door, sending a furious Knock Out fleeing into the distance.
Knock Out and Starscream then consulting about what they need to do on Megatron due to his vegetative state until they caught Bumblebee and Arcee uses Cortical Psychic Patch on their leader. They failed to catch the Autobots whom escaped, but not before knocked Megatron's life support system off. However Soundwave pointed out they could not let Megatron die by an Autobot's hand, so Knock Out was forced to reconnect his life support. Later, he noted to Starscream that Megatron was no longer showing any brainwave activity, unaware that Megatron's spark has possessed Bumblebee by accident.
Whilst he and Breakdown helping Starscream's latest plan in uncovering Energon, they were overpowered by Autobots and failed. By the time this happens, he witnesses that Megatron has returned.
He faced off against Ratchet in the episode, Stronger Faster. He was outsmarted by the Autobot but managed to get some synthetic energon.
Knock Out was sent to retrive a relic from the Iacon hall of records in New York City which turned out to be a Phase Shifter, which resulted in him having to retreat after getting badly banged up at the hands of the Autobots and their human allies. Knock Out then redeemed himself when he borrowed Soundwave's Sonic Resonator to secure one of the four Omega Keys, and heap some hurt on Arcee and Bumblebee. After C.Y.L.A.S. joined the Decepticons and ultimately failed to win Megatron's favor, he ended up being Knock Out's guinea pig which Knock Out relished with sadistic glee. Later when Starscream was welcomed back into the Decepticon fold after delivering all four Omega Keys to Megatron, Knock Out surgically installed the Starscream clone's slightly damaged yet functional T-Cog into Starscream.
In season 3, Knock Out along with Starscream unintentionally unleashed a horde of Terrorcons after injecting C.Y.L.A.S. with a chemical cocktail of Synthetic and Dark Energon which resulted in the loss of the Insecticon horde and more than half the remaining Vehicons. Knock Out was then ordered to hand over all of his science projects to Shockwave after the Terrorcon incident, and then became nothing more than a lab assistant for Ratchet and Shockwave who were working to complete the Synthetic Energon formula. After Megatron's demise at the hands of a resurrected Bumblebee, and the restoration of Cybertron with the use of Cyber-Matter, Knock Out decided to join the winning team until Miko Nakadai punched his lights out using the Apex Armor.
In the movie Predacons Rising Knock Out was held prisoner aboard the Nemesis, eager to earn Bumblebee's trust, he told them to try the Darkmount Citadel first so the Autobots could find Shockwave's secret laboratories in the hopes of capturing both Shockwave and Starscream. Later when the Autobots were on their way to use the Nemesis to fight Unicron and his leigion, Starscream liberated Knock Out and the remaining Vehicons to take the ship to escape Unicron. Knock Out then turned the tables on Starscream by using the Phase Shifter to take the Immobilizer from him and used it like a club to subdue Starscream.
- After the episode Shadowzone he was not seen for a while due to Breakdown and Starscream needing more screen time and development. He was seen again in the 21st episode and nearly every episode after.
- A running gag is that he always gets his finish scratched, pounded and even painted by a Transformer followed by Knockout complaining and throwing a tantrum about it.
- He is partners and best friends with the Decepticon brute Breakdown, and is irritated by the fact that Silas has desecrated his body by fusing himself with the remnants of his spark.
- He has sadistic tendencies as he enjoys causing others (especially Autobots) pain.
- During the BotCon 2011 panel, it was implied by the writers of Transformers Prime that Knock Out is homosexual, and that the Decepticons follow a "don't ask, don't tell" policy (meaning they are prohibited from disclosing or discussing homosexual relationships).
- In the IDW comic series, Knock Out is in a relationship with a fellow Velocitronian (modeled after Prime's incarnation of Breakdown), as confirmed by Mairghread Scott.