"Let's Fight to the End" is the 18th & 19th episode of Season 3 of OK K.O.! Let's Be Heroes and the 110th & 111th episode overall. It is a 22-minute special episode. It is the penultimate episode and the second and third episode of the Plaza Tournament one hour special event.
When a fighting tournament is announced at the Plaza, there is more at stake than meets the eye.
After T.K.O destroys the Pow Card factory, a fighting tournament is announced at the plaza to help restore everyone's power levels. K.O., who is still inside in his subconscious, is determined to take back control. When Shadowy Venomous makes it clear that he's going to destroy the world, Rad and Enid come into the tournament stadium for one last stand.
T.K.O finishes both Enid and Rad. Afterward, they find Fink and she tells them about the Turbo Collars. Rad and Enid are suspicious, but they take them anyway, following the debut of Trad and Tenid. They get back to the fight and continue as T.K.O is beginning to lose power. Shadowy Venomous finds the Lakewood tree and brings it to the surface to make T.K.O stronger. T.K.O has the power from the Glorbs which makes him stronger than before, and Trad and Tenid get kicked out of the ring. In the meantime, Boxman, the Boxmore bots, and Dendy try to fight him as well but failed after being launched into the sun.
Now that T.K.O has more power, Shadowy Venomous reveals he was only using him for his powers, enraging T.K.O, causing him to attack Venomous. Meanwhile, K.O in his subconscious found T.K.O's house, and he found T.K.O's secret box in the sandbox. He pulls it out and finds an old tape recorder he had when he was younger. He began to play it, turning it to max volume.
T.K.O takes out Fink and Venomous and begins to attack the plaza. Hearing the music, he gets angrier and angrier. Enid, Radicles, Carol, and Gar huddled together, and T.K.O shoots them with his powers, defeating them. T.K.O stops and goes back to the mindscape. When the song stops, K.O rushes over to T.K.O and hugs him. The two talked it out and finally realized that T.K.O isn't a separate person. He is a part of K.O, and K.O is a part of T.K.O, and the two fuses to become M.K.O. M.K.O wakes up and finds the whole plaza destroyed.
The President of the Universe appears to declare K.O. the winner of the tournament. He grants K.O. a wish. K.O.'s wish was "to let everybody live their best life." With this, the plaza is restored and all the heroes return, celebrating their victory. K.O. enjoys his moment with the gang and continues to live his best life.
- Turbo Enid/Tenid (debut)
- Turbo Rad/Trad (debut)
- President of the Universe
- Dynamite Watkins
- Shadowy Venomous
- Shadowy Figure
- Professor Venomous
- Ms. Mummy
- Ted Viking and Foxy
- Diving Belle
- Combo Breaker
- Puck Reverie
- Lord Boxman
- Mega Football Baby
- Bell Beefer
- Red Action
- Dolph Finn
- Joe Cuppa
- Miss Quantum
- Mecha Maw
- Baby Teeth
- Crinkly Wrinkly
- Glitter Starlight
- Rex Th' Bunny
- Mr. Logic
- Koala Princess
- Demon Queenie
- Miss Pastel
- Punching Judy
- Punching Trudy
- Jack Whacky
- Big Alligator
- Pink Turtle
- Gerald Nametag
- Bomber Fan
- Nick Army
- A Real Magic Skeleton
- Shy Ninja
- Billiam Milliam
- Billiam's Bodyguards
- Chameleon Sr.
- Cool Sun
- Corn Shepherd
- Max Collins, Jeremy Polgar, and Takafumi Hori are guest animators for the episode.
- Toby Jones said in a Twitter post that he drew in the Nick/Joff proposal.
- The episode plot about the tournament arc would have been an idea for a movie if the show had one but Ian wanted do it immediately.
- On June 22, 2019, Ian posted a board for this episode.
- According to one of Danny Ducker's storyboards, Wally the White and Biki were originally supposed to appear in the tournament fighting against each other. However, their scene was cut.
- T.K.O.'s disempowerment ray was originally supposed to have the characters to fade away "to disempower everyone so thoroughly not even a speck of dust will remain" was thought too intense for the network approval.
- The final scenes of the episode was a direct nod to Geneva's and Mira's boards from "Just Be a Pebble".
- This episode continues after "Dendy's Video Channel".
- Combo Breaker and Neil still seem to be partners since the events from "Sidekick Scouts".
- When K.O. wished that everybody gets to live to their best life, the main Jethro gets to live as the Jethro from "I Am Jethro".
- When he and Fink attack the planet, Professor Venomous wears the Laserblast helmet. He wore it first time in "Big Reveal".
- The Boxbots form Boxmore Prime again, this time with addiction of Jethro. They formed it first in "Dendy's Video Channel".
- When the heroes return, thanks to K.O.'s wish, Nick Army can be seen proposing to Joff. They are seen getting married in the next episode.
- When K.O. accepts that T.K.O. is him and he is T.K.O., this acts as a reference to the Persona franchise such as Persona 4 when a person accepts their shadow.
- When T.K.O wrestled Pird, he did the infamous "You Can't See Me" taunt by WWE wrestler John Cena to Rad and Enid.
- When Rad first turns turbo, he can be quoted saying "Get ready, little man". This can relate to Sugilite's, from Steven Universe, words after appearing and showing Steven what she can do, which were "You like that, little man?"