- "You hear that? Get ready for high school next year because you're going to be in a world of pain."
- ―Kenny to Anthony[src]
Kenny is the younger brother of juvenile delinquent Shawn Payne. After being the subject of intense bullying, Kenny seeks help from Shawn's friend Robby Keene, who becomes a mentor to Kenny. He turns to karate as a way to defend himself. However, he is corrupted by Cobra Kai's teachings, going from being bullied to bully.
Kenny is the second-born son of a US Army soldier and an unnamed mother, and the younger sibling of Shawn. One night, Kenny witnessed one of Shawn's friends stealing money from the Payne family. He tried to stop the boy but wasn't strong enough, so he ran away. Shawn intervened to protect Kenny and ultimately beat his former friend. Shawn was taken to Sylmar Juvenile Corrections to serve out his sentence.
Kenny plays an online video game called Dungeon Lord as he gets ready for school. He is dancing while waiting for the bus, oblivious to the fact it pulls up. When he turns, he sees the students laughing at him for his dance moves. Anthony LaRusso then verbally bullies him on the bus. In gym class, Anthony guards Kenny but scores a layup against him, showing that he is skilled in basketball. Things worsen when Kenny accidentally checks a basketball into Anthony's face, albeit after Anthony had mocked him. Lia, a fellow classmate, diffuses the situation and is friendly towards Kenny. After school, Kenny talks to his dad, who is in deployment at a military base in Qatar. He admits it's difficult moving in the middle of the school year and making new friends. His father encourages him to give it time, be patient with his hard-working mother, and reminds him that while unfair, Kenny has to be the man of the house now.
Later, Kenny is playing Dungeon Lord when he is messaged by what he believes to be Lia. He is surprised, but willingly accepts her friend request. During their chat sessions, Kenny opens up to Lia about the things he is into, including music, and cosplaying his Dungeon Lord character. Lia offers Kenny the opportunity to meet in character at Balboa Park the next evening, an event that Kenny eagerly accepts. But unknown to Kenny, it is not Lia on the other side of the computer screen, but Anthony LaRusso and a some of his friends cat-fishing him. They set an ambush for him at the park and video him in his Dungeon Lord costume and proceed to pummel him. Kenny is barely able to escape and only survives by hiding in a giant dumpster while Anthony and his friends hunt for him.
Kenny visits his brother in juvenile to talk about his recent experiences, including the cyber bullying going around since his adventure in the park, and explains that Anthony knows karate. Shawn laughs off the statement and guides him to Robby Keene, a former juvenile inmate, in order to learn karate to defend himself.
He goes to the Cobra Kai dojo to find Robby. When he does, he reveals to him that he is Shawn's brother much to Robby's surprise. Kreese tells him he needs to prove his worth and has him fight Kyler Park but ends up backing down after constantly getting laughed at and ends up leaving in the process. Robby goes to his house to return his backpack but after he sees a video of Kenny opening his locker with milk, he teaches him a couple moves and advises him to use his speed to come at his enemies. Robby also tells him that he doesn't believe he's Shawn's brother but Kenny adds that he is big and strong and he's fast. He comes back to the dojo but he backs down again. Kyler then makes fun of him which causes Kenny to go up and punch him without Kyler noticing. Kreese then tells him that the punch wasn't enough and had his chance to join the dojo. He then leaves but after receiving approval from Robby, Kenny earns his spot, with Kreese allowing him to join the dojo.
While on a field trip at West Valley High School, he is insulted by Nathaniel and Bert due to his affiliation with Cobra Kai. He attempts to punch Bert but is stopped by Hawk, who warns him to leave Cobra Kai while he still can. During his time in the dojo, he goes with his classmates to a drive-in to watch Bloodsport. Kyler asks him to get multiple snacks with Robby asking for one as well. After getting his food, he again encounters Nathaniel and Bert, who were also at the drive-in. He walks away but backs into Hawk and knocks over his food. Robby notices this, and a confrontation ensues between Miyagi-Do, Eagle Fang, and Cobra Kai. Miguel tells them to meet in the baseball diamond but Miyagi-Do and Eagle don't show up. When Kenny and his classmates arrive, they end up getting drenched by the sprinklers.
While changing from P.E., Kenny leaves his clothes behind but Anthony steals them. He chases Anthony and his friends but ends up running out in his underwear, causing everyone to laugh at him. During a lesson in Cobra Kai, Kenny is then ordered to spar with Robby. After Robby apologizes for kicking him, Kenny takes advantage of this weakness per Silvers' advice, and then wins the fight by leg sweeping him. Back at school, Anthony tries to reconcile with him and put the bullying behind them, but Kenny doesn't forgive him and calls him "LaPusso". He calls him the name again and Anthony and his group chase him. They end up in the library where Kenny hides and the group hopes to trap the boy. However, Kenny turns off the lights and the group splits to find him. While looking for him, Kenny attacks the group one by one. He intimidates Anthony by calling him "LaPusso", scaring Anthony, who falls down. Kenny runs up and grabs Anthony but are caught in the process. While in the office, Anthony is suspended but Kenny is off the hook. Kenny tells Anthony he got him with a smug smile on his face.
On the day of the All-Valley tournament, he fights Nathaniel and defeats him using the Miyagi-Do drum technique. He then advances to fight his own classmate Robby in the quarterfinals. He wins the first point when Robby goes easy on him, but proceeds to lose when Robby decides to win so his dojo can have a chance of winning. Kenny runs off the mat after losing with a bloody nose. As he tends to his wound in the locker room, Anthony arrives and tries to apologize again for his bullying. However, still angry over the bullying since at this point he has become a fully-fledged Cobra Kai, Kenny doesn’t forgive him and instead lashes out at Anthony and proceeds to brutally beat him up, but is stopped by Robby. Kenny threatens Anthony to wait for high school where he will experience more pain, smiling evilly at the warning. Robby reprimands Kenny as this isn't how he taught the boy. Kenny snaps back with Cobra Kai's "no mercy" mentality. At this point, Robby realizes that his mentorship with Kenny has now turned him into a corrupt individual. During Robby's fight, Kenny tells Robby to finish Eli but gets distracted and Eli recovers himself. In the end, Robby loses, causing Eli to become the boys champion. Nevertheless, Cobra Kai becomes the grand champion for the second time in a row when Tory beats Sam in the girls' finals. Kenny and the rest of his teammates celebrate and get on the mat as Tory wins. He later joins them once more when Kyler decides to schedule a party at his house to celebrate, though he is unaware that Silver bribed the referee to ensure Cobra Kai would win the tournament.
Kenny is a bright-eyed and happy-go-lucky kid who enjoys the niche of video games, anime, music, and dancing. He's a generally happy kid, despite the unfortunate circumstances around his past and his brother's incarceration. His first day at his new middle school introduces him to bullying that only increases with time. He finds friendship in Lia, a girl from school. Kenny's bullies use this connection to catfish him online, lure him to the park in cosplay, and attack him. This crushes Kenny emotionally and he barely escapes the bullies, hiding in a recycling bin to avoid their onslaught of attacks.
As his confidence wanes, he confides in Shawn, who suggests he find Robby Keene to help. Under the guidance of Robby, Kenny learns to not run away from his bullies, flinch from danger, or be afraid of others. He gradually gains confidence in himself and his martial arts. He joins Cobra Kai Dojo and finds allies in the older students, and a mentor in Robby. The longer Kenny is exposed to the vicious mentality of Cobra Kai, the darker his personality becomes. He learns how to manipulate his enemies and strike first, but also to take control of his life. While this makes him a stronger fighter, he loses sight of the guidance Robby gave him. He rejects Robby's condemnation of his antics by citing that he's Cobra Kai. This allows him to turn the tables on his bully, going from being the bullied to the bully.
Kenny is the smallest student in Cobra Kai and in his school. This makes it easier for his bullies to restrain him and attack. His first instinct is to run away from the attackers due to his speed. With Robby's guidance, Kenny learns to use his speed to attack, not run away. He combines strong punches with a fast speed to attack larger foes. Kenny works hard to overcome his flinching and instinct to run away. When he does, he becomes a capable fighter who reaches the quarter-finals of the All Valley Karate Tournament. He loses his match to a much stronger and more experienced Robby, but easily beats Anthony LaRusso in the locker room. Despite only being in Cobra Kai for a short time, he quickly picks up skills, which could mean that he is gifted or a quick learner.
Kenny meets Robby at Shawn's behest, as Kenny needs Robby's help against the bullies targeting him. Robby sees an opportunity to take the boy under his wing, becoming the mentor that he never had growing up. He teaches Kenny to use his speed as a weapon, defend himself from attackers, and ultimately, help him earn a spot in Cobra Kai. Robby continues to look out for the boy, assuring him that the other student will come around after the hazing. He becomes protective over Kenny, with Kenny seeing Robby as a protector and someone to be trusted. Robby retaliates against Hawk for picking on Kenny at school by shaving Hawk's signature hairstyle. During a training exercise to find and target weaknesses, Silver specifically chooses Kenny to fight Robby. He knows Robby cares for the boy and won't be capable of hurting him. Silver's assumption is correct, ultimately leading Kenny to manipulate the kindness by faking an injury and winning the exercise. As Robby becomes distracted in his personal life, Kenny slips deeper into the mentality of Cobra Kai and the teachings of John Kreese. During the All Valley Karate Tournament, Robby sees Kenny cheering for him to hurt Demetri. While Robby ultimately does defeat Kenny in the All Valley, he does it knowing it's the only way to advance to the next stage. He later has to pull Kenny off Anthony LaRusso, chastising him as this wasn't how he taught Kenny. Kenny rejects his teachings, citing the Cobra Kai mantra, before threatening Anthony. Kenny also tells Robby to finish Eli but he gets distracted, allowing the latter to break free. Later, Robby emotionally admits to Johnny how he wanted to be there for Kenny, but watching the boy at the tournament and in the locker room was like looking into a mirror. After seeing him become corrupt, he feels he's messed everything up.
Kenny has been the victim of Anthony's bullying. They first meet when Anthony makes fun of his dancing while waiting for the bus. While in gym class, Anthony guards Kenny but he ends up letting him score a layup. In the next possession, Kenny accidentally checks a basketball into Anthony's face, albeit after Anthony had mocked him. At one point, Anthony steals Kenny's clothes in the locker room, resulting Kenny being embarrassed in front of his own classmates. Because of this, Anthony tries to apologize for bullying him but doesn't forgive him and calls him "LaPusso". He calls him the name again and Anthony and his group chase him. They end up in the library but Kenny attacks them one by one. He says LaPusso and then beats up Anthony but are caught in the process. While in the office, Anthony is suspended but Kenny is off the hook, resulting in Anthony being grounded by losing video game privileges and sent to his own room as a result. Anthony then watches the tournament and is shocked to see Kenny lose his match to his classmate Robby Keene. When he goes to the locker room, he admits his mistakes and tries to apologize to him again but is then brutally beat by Kenny, threatening him that he will be in a world of pain once they go to high school.
- Shawn Payne (Brother)
- John Kreese and Terry Silver (Senseis)
- Kyler Park (Frenemy/Friend)
- Tory Nichols (Friend)
- Lia Cabrera (Friend/Crush)
- Zack Thompson (Bully/Enemy)
- Marcus and Slade Wang (Bullies/Enemies)
- His Dungeon Lord Legacies screenname is Kennythejet99.
- In his free time, Kenny draws anime, listens to music, and does Dungeon Lord cosplay on occasion.
- His favorite Dungeon Lord character is Dr. Scribblebottoms.
- Kenny's address is 1623 Otsego Street, Encino California, 91436.
- Anthony bullying Kenny about Lia is similar to how Johnny bullied Daniel about Ali.