This is a common Stock Phrase utilized in a work of the action genre, mostly used by someone who up to this point in the plot has been ineffectual compared to his or her highly trained or super-powered friends.
They may even have been The Load to their companions - such is their supposed uselessness in combat - but should they be the last man standing when all their warrior companions have fallen to the invincible might of the Big Bad, busy giving their obligatory Hannibal Lecture and gloating at their impending doom, the Power of Love or Power of Friendship will kick in and kick in hard.
Staggering from his or her own grievous physical (and often emotional wounds), the good hearted Every Man takes a deep breath and shouts on the top of his or her breath "You leave him/her/them alone!" and gains the Heroic Resolve to righteously kick the ass of evil that dared to lay its hands on their beloved friends.
This is the turning point of a character that will can earn the respect of the other characters (not to mention the audience) often combined with Crowning Moment of Heartwarming. They may end up as the Chekhov's Gunman or at least be using a Chekhov's Skill. Tragically, this burst of heroic resolve will often not be able to compensate for their lack of practical combat experience and/or lack of power, so this trope will also often overlap with Heroic Sacrifice.
- A Certain Magical Index
- Epically invoked by Kamijou Touma as he challenges the seemingly invincible Accelerator in order to rescue Misaka Imouto.
- Just when you thought Kamijou Touma couldn't one-up that, he does in New Testament Volume 9 where he essentially does this to the entire world after he decides to save Othinus.
- Invoked by the first time by four year old Son Gohan of Dragonball Z as he demolishes his uncle Raditz, stopping him from beating his father Son Goku to death.
- Saten Ruiko in A Certain Scientific Railgun as she smashes the Capacity Down device paralyzing her friends, just in time to stop Therestina from killing them.
- Mamori does this in defense of Sena all the time in Eyeshield 21 up until Sena reveals himself to be the running back of the Devil Bats.
Films — Animation
- Russell in Up as he gains the Heroic Resolve to save Carl from evil biplane flying dogs.
- Soren in Legend of the Guardians: The Owls of Ga'Hoole tells Nyra "You leave her be!" when the evil owl taunts Gylfie.
- In Balto 2, Balto snarls at Niju "Leave them be!" when the latter tries attacking Aleu for defending Nava. This helps a lot since his (literal) Papa Wolf mode activates right away.
- When Wreck-It Ralph sees the other Sugar Rush racers bullying Vanellope, despite not liking her before, he yells "HEY! LEAVE HER ALONE!" and runs down the hill, yelling and roaring until they flee.
Films — Live-Action
- What Dave, an Adorkable teenager with no fighting skills whatsoever shouts to give himself the courage to defend a mugging-victim from being murdered by three thugs in Kick-Ass
- Shaun in Shaun of the Dead, as his Too Dumb to Live friend is doomed by the bites of a swarm of zombies.
- Ripley's ultimate Mama Bear moment in Aliens: "Get away from her, you bitch!"
- The Brady Bunch Movie features the original Peter Brady, Christopher Knight, in a scene as a coach who stops two boys from thoroughly bullying the movie Peter:
Coach: Hey. Do it, and die.
- "Her" instead of "him" was used by George McFly in Back to the Future, standing up to the school bully for the first time. While possessing the resolve, he seems to lack the confidence and the physical prowess, at least for a few minutes until he manages to land a solid left hook.
- Not so impressive example from The Last Airbender: Katara says this line when she runs over and shoves a Fire Nation guard who had been mocking Aang. The not so impressive part comes from the fact that after she shoves him, no one does anything for about a minute, and ultimately Aang has to use his Airbending to throw the guard away when he attacks Katara.
- In Galaxy Quest, Jason Nesmith says this to Big Bad Sarris when the latter is torturing the leader of the Thermians.
- Samwise Gamgee to Shelob in The Return of the King. "Let him go, you filth. Let him go! You will not touch him again!"
- Subverted for laughs in Doctor Who, "Amy's Choice", when The Dream Lord threatens Amy:
Doctor: Leave her alone!
Dream Lord: Do that again. I love it when he does that. Tall, dark, hero... "Leave her alone!"
Rory: Just leave her.
Dream Lord: Yes... you're not quite so impressive.
- Fred does this in "The House Always Wins" on Angel when the guards at the casino beat on Gunn,though she gets a gun pointed at her just after. It's Angel who saves the day.
- Giles, high on magical candy, gets one on on Buffy the Vampire Slayer in "Band Candy", when one of the mooks at the candy factory goes after Joyce.
- Star Trek: Voyager, "Cold Fire": When a Sufficiently Advanced Alien keeps pushing Kes to join them and not worry about the death of the Voyager crew, Neelix yells, "Leave her alone!" and runs at him. It doesn't take, but seeing him thrown backwards by her harasser causes Kes to get dangerous.
- Played for laughs in Good Morning, Mrs. Butterworth Two and a Half Men'', where Alan points out to Charlie that he needs him to keep Chelsea occupied. Charlie admits that he's right, but realizes that his dummy is expendable and threatens to do away with him unless he stops "text-blocking" him.
Alan: Just let him go, Charlie. This is between you and me.
Charlie: (holding the dummy by its head) Not anymore.
Alan: Don't you dare hurt him!
Charlie: Well now, that's entirely up to you. His tiny wooden head is in your hands.
- In Series 2 of Marcella, the titular main character finds the Serial Killer, Jane Colletti, she is been hunting for the Story Arc, after she has kidnapped her son Edward, just as she is about to lobotomise him. Marcella responds by taking Colletti's own daughter hostage at knife-point and demanding with white-hot fury she gets away from her son.
- Mission Vao recalls calling this out to some thugs who were harassing Zaalbar and charging them, in Knights of the Old Republic. Being about twelve at this point, she gets pummeled pretty badly. Of course, this ticks off Zaalbar and he wipes the floor with every last one of them. The two have been best of friends ever since.
- Anyone playing the BBL route in Hatoful Boyfriend who's seen Yuuya's route knows that he's a Teen Super Spy, but otherwise he comes off as a Chivalrous Pervert at best. And then there's BBL. Less of a physical turning point, but it and what it leads to causes a radical shift in how he's seen as a character.
"Stop that, Isa! I told you not to touch my brother."
- In The Inexplicable Adventures of Bob!, Galatea goes berserk on Riboflavin, screaming "Stop hurting my uncle, you wretch!"
- In Teen Titans, Raven is given the job of bringing three young potential superheroes to a safety place and Hilarity Ensues while she tries to keep them away from the danger chasing them. During the episode's climax, Mallah gets the upperhand on Raven, prompting the kids to yell, "Hey, you big ape! Why don't you Pick on Someone Your Own Size?" and they use their innate powers to kick ass.
- In The Superhero Squad Show episode "Planet Hulk": the Hulk, exiled to another planet by the Dark Surfer, sees a group of Brood delivering a Rodney King-type beating to one of their kind; roaring "You leave little bug alone!" the Hulk delivers a SERIOUS ass-kicking.