Has a villainous example in Dina Araz. First she goes rogue against a terrorist organization, including her husband, when they order her son Behrooz to be killed. Then she turns around and tells Jack Bauer she'll be happy to let every nuclear plant in America melt down if he doesn't rescue Behrooz from a hostage situation. Don't. Touch. Behrooz.
Ahem, Jack's wife, Teri? She allows herself to be raped to spare her teenage daughter Kim, then we find out it's a ploy to steal his phone. Later, when the rapist goes to execute them, Teri shoots him, then fires a second shot to make the terrorists think she and her daughter were executed.
Babylon 5: Delenn during the secession. Also to merchant shipping in the episode lines of communication. And to Dukhat. Watching her in a Mama Bear rage is as beautiful as watching a volcano.
Athena in the revised show goes murderous on Natalie, a Six model Athena believes wants to kidnap her daughter Hera. To quote a reviewer:
"Ordinary moms don't play when it comes to the safety of their children, let alone trained warrior alien robot moms."
Earlier in the series, Roslin decides they'll have to forcibly terminate Athena's unborn child. A truly epicUnstoppable Rage ensues when she finds out, to the point that she's headbutting bulletproof glass so hard it breaks, with no discernible effect on her beyond some bleeding.
There's also Kara Thrace. She initially freaks out at the sight of the child because of her own Mommy Issues, but goes Mama Bear with a vengeance and stabs a Cylon dead to keep her safe. And then it turns out that the kid isn't really hers, after all - Cylon #2 was just playing mind games with her using someone else's stolen toddler.
Laura Roslin could also be considered this for the entire human race, given her tendency for airlocking Cylons and attempting to abort human/Cylon fetuses to protect the fleet.
Being Human: This BBC3 Program when Annie entered the warehouse full of old, and powerful vampires and screamed "GIVE ME BACK MY FUCKING BABY" and defeated the old ones and then to save the world actually BLEW UP the child in question. Now that is motherhood.
Buffy's mom Joyce, who goes after Spike with an axe when he threatens Buffy.
Buffy herself, who goes nuts at the Knights of Byzantium, Well Intentioned Extremists who want to kill her younger sister in order to save the world.
Glory, for the same reason. Glory was strong enough to make their earlier fights Curb Stomp Battles, but in the final one you get the feeling Buffy's getting a lot of catharsis slamming that magic hammer at her head over and over again.
It's a Summers thing. See Dawn's response to Spike in season 7.
Dawn, to Spike: I know I can't take you in a fight, even with a chip in your head. But if you hurt my sister, touch her at all? You're going to wake up on fire.
Spike, later, to Buffy: When did your sister get unbelievably scary?
In Season 9, a demon goes after Willow and Marrack after Willow kills her child.
Has Maddie Westen, who seems like any regular kind, gentle elderly woman. However, threaten her sons and she will make you regret it.
Take as proof the time that she made an enemy agent tell her where Michael was without doing more than offering him a cigarette and kindly and apologetically telling him You Have Outlived Your Usefulness and hopes they will make it a quick death this time, when the combined efforts of Sam and Fiona couldn't break him. And she's not even a trained spy, she's just a True Companion.
When a young boy to whom she had grown attached was screaming in pain, Piper put every effort into her power of explosion and managed to break through an impenetrable fence. The act caused her sister to comment, "I think we just saw a mother lift a car off her child."
After Auntie Paige's failed attempt to locate newborn Wyatt's would-be kidnapper nearly got her killed, Mama Bear Piper burst into the demon Black Market, shouted "WHICH ONE OF YOU DIRTBAGS PUT A BOUNTY ON MY BABY!!" and proceeded to blow the place up.
Before this, when the guard demanded to know who she is, her answer before blowing him up defines the very essence of this trope.
Piper "I'm the mother!"
What's even more awesome is that this causes the underworld a collective Oh Crap moment, and immediately afterward they send a representative to the sisters, swearing that no demon will be allowed to even think of touching Wyatt without being violently reprimanded, to prevent Piper from entering Mama Bear mode again.
All three of the sisters could be seen as Mama Bears, when Wyatt and Chris are threatened. And they're this even to each other.
Grams had shades of this as well.
Chicago PD: Detective Erin Lindsay shows some Mama Bear tendencies towards Nadia, one of her witnesses and CI, a seventeen-year-old drug addict. These include but are not limited to: threatening the guy holding her at gunpoint, promising to take care of her when she has withdrawal symptoms, letting her stay in her apartment, urging her to get clean, and taking her back to the clinic after Nadia participated in an undercover mission and promising to check on her every day.
The Cosby Show: Denise Huxtable Kendall mistakenly believed her mother-in-law couldn't stand her. Believing herself unable to please the woman left Denise a crying wreck. Luckily for everyone involved, her mother Claire was wise enough to verify Mrs. Kendall's actual opinion of Denise before unleashing a Mama Bear fury (turns out hubby Martin's mother couldn't stand Martin's frequent rushes to judgement in matrimonial situations). For not listening to his mother, Martin was...less lucky.
Sondra inherited this from her mother. "Day of the Locusts" is a more comedic example than most, but it proves that this runs in the family. She even intimidated Claire.
Criminal Minds: JJ beautifully demonstrated in the season seven finale that you don't ever threaten Henry or Will. That UnSub had it coming.
Brought up in one episode, when the team is discussing a recent case where a man was killed on a plane by the passengers when he went berserk and tried to open the plane door.
Nick: Do you think you could ever take a life in that situation?
Catherine:*answering instantly* I could.
Sara:*shocked* You didn't even stop to think about it!
Catherine: When it comes to the life of my child, I go all the way.
Then there's the episode where Catherine's ex is murdered and Catherine has to fish Lindsay out of a car that's rapidly filling with water in a flood channel. When a suspect (her ex's main squeeze) starts referring to Lindsay as a "little brat" and reveals she left her in the car, Catherine storms in and nearly takes her head off.
When she came home to find a suspect in the driveway talking with her mother and daughter, she very calmly tells her mother to take her daughter inside, then she punches the guy in the face and pulls a gun on him. "You came to my house." Don't ever mess with Catherine's kid.
CSI NY: Lindsay goes full-on Mama Bear when she wakes up in the middle of the night to find that Shane Casey, the serial killer who has been stalking Danny not only has him at gunpoint, but is also holding their daughter, Lucy. He threatens to kill the baby if Lindsay doesn't drop her gun, but Lindsay responds by shooting him dead.
In a later episode, she gets hit on the head by a vending truck while trying to protect Lucy from a panicked crowd and a man shooting. She'd rather get a hairline fracture of the skull than let her little girl get hurt.
Degrassi: Mrs. Torres. Overlaps with My Beloved Smother - she's quite controlling of her football-jock older son and still coming to grips with her younger son'stransgenderism, but if anyone else messes with them she will make their life miserable (and the school principal's as well, for good measure).
In the second season, despite all of the emotional and mental distress her daughter Danielle put her through, Bree goes full-out Mama Bear when Danielle is revealed to be on the run with a murderer - one of the new neighbors and her boyfriend no less!
In a recent episode, Susan punishes Gaby's daughter, Juanita, for pushing and bullying her own son, MJ. Gaby, for all of her insecurities over Juanita's weight, gets fiercely protective of her daughter and starts calling MJ a little girl, to put it nicely. Cue the Mama Bear catfight.
Jackie Tyler WILL carry a HUGE gun and actually kill Daleks if it means saving her daughter Rose. Also from the series Amy Pond. She was going to take down a whole spaceship with crew, with her and her husband inside, just to save her daughter.
Madame Kovarian: [With her eye-patch giving her a direct link between herself and her bosses who are using said link to torture her] Amy...Help me.
Amy: [Rips off her eye-patch] You took my baby from me. And hurt her. And now she's all grown up and she is fine, but I'll never see my baby again.
Madame Kovarian: ...But you'll still save me, though. Because he would, and you'd never do anything to disappoint your precious Doctor.
Amy: ...The Doctor is very precious to me, you're right. But do you know what else he is, Madame Kovarian? Not here. [pushes her eyepach into her eye while she screams] River Song didn't get it all from you...Sweetie.
Madge Arwell, from the 2011 Christmas special, definitely fits. She's a recently widowed woman from 1941 lost in a forest on an alien world at some point in the future with three soldiers pointing giant guns at her. Naturally, she starts crying and, seeing how upset she is, the soldiers drop their weapons so she can compose herself enough to answer their questions.
Head Soldier: We're from Androzani Major. The year is 5345, and we mean you no harm. Where are you from?
Madge: England, 1941. *pulls gun* And there's a war on. Crying's ever so useful, isn't it?
Head Soldier: If you say so, but there's nothing you could say that would convince me you'd ever use that gun.
Madge: Oh, really? Well, I'm looking for my children.
Dollhouse: Do not screw around with any of the Dolls. They're not her blood children, but Adelle DeWitt responds to the harming of a Doll with enough cold brutality to make anyone wince.
She's also become like this with Topher in the After the End finales "Epitaph One" and "Epitaph Two: Return." When Zone begins to mock him, she is not pleased.
A particularly scary Mama Bear appears in Elementary. In the episode "The Diabolical Kind," a little girl is kidnapped from her wealthy parents' home and held hostage by a gang of criminals that used to work with Moriarty. An Enemy Mine situation begins, with Sherlock, Jane, and Moriarty working together to rescue the girl; as a safety precaution, Moriarty is forced to wear a set of powerful handcuffs that administer a shock if the person wearing them tries to escape. As it turns out, the girl is actually Moriarty's daughter, who she left with the wealthy family rather than raise the child herself; she was kidnapped to taunt and extort the master criminal. When Moriarty finds out about this, she cuts open her wrists with glass to disable the handcuffs, escapes her prison cell, and brutally kills the men who took her daughter, saving a special, drawn-out torture for the leader of the scheme. That's right: one of the most brilliant, resourceful, and dangerous criminal minds in the world has a child. If you value your life, do not mess with that child.
Eureka: One episode begins with Tiny, a NASA-commissioned Titan rover, chasing Carter, Fargo, Grant, and Alison's son Kevin. When the episode returns to this scene at the end, it ends with Kevin pinned to the ground, Tiny looming over him, and resident Mama Bear Alison yelling "Get away from him, you bitch!" It's not until Tiny repeats the line back to Alison that everyone realizes that Tiny wants EMO, a little robot with emotional attachment programming that was to be Kevin's parenting class assignment. Tiny had downloaded said programming earlier that day, and bonded with EMO when it wandered into her storage lab. But she had NOT given consent to her new "baby" going camping with the guys.
Everybody Loves Raymond: Nagging, overbearing, and irritating though she may be, do not ever mess with Marie Barone's sons if you want to keep your dignity intact. Robert's first wife Joanne found that out the hard way.
Farscape: Despite being a Team Mom rather than anybody's biological parent, Zhaan certainly has her moments. Case in point, her reaction to the being responsible for building Moya threatening the lives of both the ship and Pilot: suck him through a jet engine!
Don't forget about Aeryn in "The Peacekeeper Wars". Ahkna threatens her unborn child, Aeryn gives birth and proceeds to shoot Ahkna in the head.
Every female on Serenity is a Mama Bear to Kaylee - Zoe rips Mal a new one for hurting her feelings, River takes out three Alliance soldiers with her eyes closed after Kaylee is too scared to do so herself...the only exception is Inara, who seems happier to baby Kaylee and brush her hair. Moral - don't. mess. with. Kaylee. It will NOT end well.
Even if none of the Mama Bears get you, there's also several very large, and very well armed Papa Wolves equally attached to her.
Catelyn Stark vows to wipe out the Lannisters in retaliation for them killing her husband and taking her daughters hostage.
Cersei Lannister is a horrible person, but she loves her children, and will reign Seven Hells down on anyone who might harm them. This is best exemplified when she's even willing to defy her father when he tries to ship her off to marry Loras Tyrell, which would leave Tommen behind to be used as a political chess piece between Tywin and Margerary.
Cersei: I will burn our House to the ground before I let that happen!
Olenna Tyrell poisons King Joffery to protect her granddaughter.
Olenna: You didn't really think I'd let you marry that monster, did you?
General Hospital: Lawyer Alexis Davis has killed more than once for one of her girls and she's not above bribery, faking a paternity test or making deals with the mob if it will help one of her children. NEVER mess with Alexis's daughters Sam, Kristina and Molly. She WILL drive over you with her car, shove you out a window or send her hitman lover to mess you up if you forget these wise words of advice.
It's odd that no one has mentioned how much of a Mama Bear Lorelai is. Anytime Rory could have possibly been hurt, let alone the time that she actually was hurt, Lorelai went from Cool Mom to panicky, overprotective "hurt my daughter and your death will be slow and painful" Mama Bear.
Good Luck Charlie: Played for Laughs. Amy met with one of Teddy's teachers to try to talk him into changing her grade on a test (he had marked an answer wrong on a minor technicality). When he brushed her off, Amy calmly knocked everything off of his desk. "Mama Bear just cleared your schedule." The next day, the principal called Teddy in to discuss the security camera footage of Amy chasing the teacher through the halls with a janitor's broom.
Hanginwith Mr Cooper: After her daughter attempts to hide the fact that she's being bullied, the genteel Southern woman Geneva, who to that point had never displayed any show of anger above a stern look, bursts through the doors of the school and screams "WHOOOOO'S BEEN MESSIN' WITH MY BABEEEEEEH???" She then threatens to "RAAAAAAAIIIIN on [the bully] like a GEORGIA THUNDERSTORM!!!!!"
Played straight: Nikki/Jessica were both devoted to little Micah and willing to do much to protect him. Jessica's methods were a bit more violent. Also, its because of her going to great lengths to protect and help her family that acted as the first clue in the Season 1 Finale that The "Jessica" that "killed" Micah before fighting Nikki was not actually Jessica, and that "Micah" was actually an illusion.
Angela Petrelli also proved to be quite the Mama Bear for Nathan Petrelli. She wanted him to succeed in being the mayor of New York City and ultimately the Presidency (although she did not anticipate that Sylar would actually take his place), and she even killed her husband when it became too apparent that he was perfectly willing to murder her son before he digs deep enough to find out some of his evil deeds, and she even goes as far to brainwash Sylar into thinking he's Nathan via Fake Memories (and essentially forcing Matt Parkman into doing so) when the real Nathan died.
Mrs. Benson moves in for her Bad AssRoaring Rampage of Revenge in iFence, beating a bunch of Freddie's bullies and other fencing students while Dual Wielding a pair of sabers. Having a freakishly protective mother may be a nuisance for Freddie, but it's a nightmare for whoever puts Freddie in danger.
I Dream of Jeannie: Jeannie certainly had her Mama Bear moment in the climax of the 1991 made-for-TV movie I Still Dream of Jeannie. (She comes to her son Tony Jr.'s rescue by blasting open a set of heavy-duty fire-rated steel doors. Sweet, giggling, kind, seemingly ditzy Jeannie then gives way to an enraged monster). Truly her Crowning Moment of Awesome.
Jeannie: DO NOT TOUCH HIM!
I Shouldn't Be Alive: This show once featured a family that got lost in the desert. The mother's boyfriend went off for help and later the mother and her two daughters tried to follow him. While they were walking, human traffickers tried to capture the girls. The mother's response: "If you hurt my children, I will shoot you." The traffickers knew better than to mess with an angry mom.
Jekyll: The female protagonist is asked when she first knew she could kill someone. She replies that it was after her children were born. The answer is the key to the nature of Mr Hyde in that he is a ruthless psychopath created not by the dark side of humanity, but by pure love.
Had one episode in which a Nanotyrannus tries to take out a pair of young Tyrannosaurs. He succeeds in killing one, but the mother arrives and kills him, ripping apart the corpse to keep any other predators away.
Also notable was the episode in which a male Majungotholus attempted to kill a baby to entice the mother to mate. While the male succeeds, the female breaks his neck, preventing him from moving as she eats him alive.
Law & Order: SVU deconstructs this trope with Detective Amanda Rollins and her sister Kim. Amanda's established as being extremely protective of her little sister, to whom she'd acted as a mother figure since their actual mother is a dysfunctional mess. Eventually, Kim uses this as part of a Batman Gambit in which she sets Amanda up to kill her abusive boyfriend in "defense" of Kim, so that she (Kim) can collect insurance money on the guy. She then frames Amanda for the entire scheme, leading to Amanda getting investigated by Internal Affairs, nearly losing her badge and facing prison time.
LOST: Claire, especially in season six when she learns that Kate was raising Aaron. And Kate herself qualifies as well in regards to Aaron.
Mad Men: When her neighbor threatens to kill Sally Draper's dog, her mother Betty shoots his beloved pigeons with an air rifle.
Major Crimes: Captain Sharon Raydor for her Foster Kid Rusty Beck. Don't fuck with him, or she will have your hide.
When Reese is the victim of a cruel prank by the popular girls in one episode, Lois strikes back (which is in fact the title of the episode) with overly elaborate and exotic forms of revenge (such as filling up one girl's motorcycle helmet with bubblegum and putting a fraudulent charge for an expensive hotel room for a sexual getaway on another girl's credit card).
In another episode, a corrupt teacher is revealed to actually have it out for Reese when Malcolm accidentally lets slip that he did one of Reese's tests for him and the teacher still gave it an "F". Lois' anger at the boys is completely dwarfed by her anger at the teacher. She proves completely willing to let Malcolm take the fall for cheating because she knows he's smart enough to succeed in life anyway; Reese needs all the help he can get.
Morgana's strong attachment towards Mordred, a young Druid boy she nurses to health, causes her to become very protective of him and a willingness to do anything for him in order to keep him from harm's way.
Morgause. Just in season 2 episode 12 she smashes a door off it's hinges and gives up her entire plan just as it was about to succeed to save Morgana's life, and in season 3 she captures Merlin and is very angry at him for hurting Morgana.
Gwen is this to Merlin. When a Lamia attacks him, sweet, gentle Gwen proceeds to scream "GET AWAY FROM HIM!", run up to said Eldritch Abomination, and stab it.
Betray her knights and she'll execute you.
Missing: This ABC show has Becca Winstone, who retired from the CIA after her husband was killed. When her son is kidnapped, she goes nuts. " I am not CIA, I am a mother looking for her son!"
My Name Is Earl: If you value your teeth, don't even think about saying an unkind word about Joy Turner's kids. She's got one mean left hook. Even happy pills can't turn off her instinct to stick up for her kids.
In one episode, a mother lays a royal smackdown on her "sister" (actually one of the kidnappers) the minute she find out that her daughter is safe. Bonus points in that the trope is actually Lampshaded by Ducky in the same episode.
"She's NOT my sister! She's ONE OF THEM! She told me if I didn't lie to you they'd KILL MY BABY!"
In "Outlaws and In-laws" Mike Franks actually names this trope directly, when telling his dead son's mother-in-law about his daughter-in-law, her daughter, shoots down two mercenaries trying to kidnap her daughter with a .22 caliber hunting rifle. Franks remarks that out of six shots, she hit with five.
Agent Lee became The Mole to protect her little sister, whom she has raised as her own since their parents' deaths. The moment she finds out the kid in question is safe, she lets Gibbs SHOOT her to take the bad guy down!
Mary Margaret kicks Jefferson out of a window as a result of her subconscious Snow White persona coming out because Jefferson was about to shoot her daughter Emma.
Once she regains her memories as Snow White at the end of season 1, she becomes a full on "mama bear" with Emma, following her through a portal to the curse ravaged FTL, saving her from ogres and putting herself between Emma and any threat.
The ogre-incident deserves special mention. With her daughter Emma about to be attacked by a twenty-foot-tall ogre, Snow put an arrow straight through the creature's eye, killing it with a single shot. You do not want to mess with this woman's family.
She was less than pleased when Mulan started hacking down the beanstalk that Emma was up, and who knows what she would've done if Emma hadn't come down just then to admit that she had in fact told Mulan to do just that.
King George/Spencer attempts to shoot at a wolfed-out Ruby. Granny shoots the gun out of his hands with her crossbow and threatens that the next one "goes between [his] eyes."
Especially in season 3. If you try to kidnap Henry, she will team up with her worst enemies and track you down in the jungles of Neverland. In Save Henry, she reveals that she feels no regret for any of the horrible things she did "because it got me my son", after which she proceeds to rip Henry's heart out of Peter Pan's chest and return it to him, saving Henry's life. Even Evil Has Loved Ones indeed.
One Tree Hill: Brooke Davis is fiercely protective of her adoptive daughter Samantha. When Sam gets kidnapped by Xavier, Brooke gets over her fears, rescues Sam, and throughly kicks his ass, then she holds a gun to his head and is the verge of pulling the trigger until Sam talks her out of it. Brooke then says she won't waste anymore time with garbage like him and then cold cocks him with the gun before walking off.
Orphan Black: Both Sarah and Alison show shades of this towards their own kids, and all the clones are very protective of Kira - as is Mrs. S. Even Helena has a mild case.
Heck even Cosima is this towards Kira and she's never even met her.
The Outer Limits: Shal in the episode Rite Of Passage. She's a perfectly ordinary human that convinces her husband to help her rebel against their alien caretakers after their baby is confiscated. The aliens did that because thay felt that they were better equipped to care for it. After realizing that it is no excuse for separating a mother from her child, they apologise and return the baby.
Power Rangers in Space: There's one episode, in which a monster is forced to be evil, but is good-hearted. After fighting with a lone Cassie, she sees the gentleness inside of him, and tells him that it's okay to be good. However, Astronema attacks the monster, severely damaging it. The look of sheer hatred on Cassie's face toward Astronema is the source of nightmares.
Pretty Little Liars: Of all people, Pam Fields from this TV series (adapted from the book series). Sure, she's trying to come to grips with her daughter's being a Schoolgirl Lesbian, but when Paige's father says that Emily became the captain of the swim team because she's a lesbian, she lets him have it. Arguably her Crowning Moment of Awesome. (Especially considering her earlier behavior towards her daughter's sexuality.)
Quantum Leap: Played with since the mom in question was actually Sam Beckett in the mom's body.
Rachel Matheson. Episode 2 showed Rachel shooting the Wiry Stranger when he put her daughter Charlie's life in danger and tried taking away the Matheson's food. Episode 7 had Rachel making a deal with Randall Flynn to make sure Danny Matheson survived. In episode 9, when Monroe threatened to have Rachel and Danny killed off and replace her with Dr. Bradley Jaffe, she responded by stabbing Jaffe to death and said that Monroe still needs her. When Danny dies in episode 11, she embarks on a journey to the Tower with Aaron. Episode 17 turns this into a Deconstructed Trope, when she reveals to Aaron that she only wants the power turned back on so that Monroe will get killed off by other people and avenge the death of her son in a sense, and that this matters more to her than the Blackmore's dying son. Episode 19 has her reluctantly team up with Monroe to save her daughter's life.
Charlie is starting to show signs of this, too. Episode 10 has her step forward and offer herself to be shot by Sergeant Will Strausser instead of Danny. She is quite protective of her brother that way.
The Sarah Connor Chronicles: As mentioned above, expounds on the fierceness Sarah displayed in the movies. Her whole life is this trope, fighting to keep her son safe from the machines sent to Terminate him. Unstoppable, unrelenting, remorseless killing machines that have laid waste to entire armies of Resistance fighters and police officers, always single-handedly - and she has buried every one. In fact, she's destroyed more Terminators than any other human. No wonder her son said she was the greatest fighter he'd ever known.
In the episode "The Dauphin", the shapeshifting guardian of a young girl destined to rule a planet (who is later revealed to be of the same species) takes this to absolutely insane levels of paranoia, up to and including ordering Dr. Pulaski to kill a patient with a mildly infectious disease because it just might possibly effect her surrogate daughter, who was not even allowed outside her quarters anyway.
Dr. Beverly Crusher can be a Mama Bear too. She came after Lore with a phaser when he threatened her son. He may be a Creator's Pet, but his mama loves him.
Star Trek: The Original Series: Horta in the episode The Devil in the Dark is a classic example of a Mama Bear. The mining colony at first believes that she is attacking them out of pure malice, not knowing that the odd silicon spheres that they've been finding and disposing of (thinking them to be worthless) are her eggs, and her attacks are an attempt to defend them. Fortunately, once Kirk and Spock figure out that she is really a peaceful and reasonable creature they can communicate with, they find she's open to a compromise to settle the conflict.
Star Trek: Voyager: Do not mess with Janeway's crew. Especially not when Janeway has the newest, most powerful technology of the Federation at her disposal and absolutely no issues with using it.
Later on, a similar prohibition applies regarding the ex-Borg kids from "Collective" and Seven of Nine. Messing with them isn't just likely to end badly for you, it's virtually guaranteed.
Ms. McCall does not react kindly to Mr. Argent's implication that her son is dragging down his daughter. In season 3, the alpha twins find themselves on the business end of a defibrillator when they threaten her son.
A darker example would be Mrs. Argent, who seriously threatens Scott with violence and in one incident TRIES TO MURDER HIM after witnessing Scott making out with her daughter.
Terra Nova: Elisabeth Shannon. Up until the season finale, she's simply an amazing mother, a brilliant scientist and an incredibly-gifted doctor. But when her son and husband are captured and tortured, she takes merely thirty seconds to out-badass almost every other character to appear in the first season. And how.
Warehouse 13: HelenaG. Wells. When her daughter was murdered, she inventedMental Time Travel to try and change the past. She failed, but put up a hell of a fight by her account. Claudia tells her that losing a daughter must be the worst pain imaginable. Wells tells her otherwise; what she did to the people who killed her daughter is the worst pain imaginable. And considering the show's track record, that line may very well turn out to be a Chekhov's Gun.
Weeds: Nancy Botwin has this as her best quality. Just thinking about hurting Silas, Shane or Stevie is a bad idea.
In Wolfblood, Maddy's mother is someone you don't want to mess with. She wolfs out when a group of older girls threaten Maddy. She's also quite scary with Rhydian when she thinks he's leading Maddy astray or risking exposure.
The X-Files: Scully has ample opportunity in season 9 to demonstrate her Mama Bear skills, since everyone and their brother is out to kidnap and/or kill William. In one episode, an assassin breaks into her apartment and locks her out of William's nursery. Just as he's about to smother the baby, Scully bursts in, guns blazing. She shoots him three times in the stomach and refuses to give him medical treatment or allow an ambulance to be called until he gives her answers about why he's after her son. Doggett gives her a What the Hell, Hero? moment over it, and she still doesn't want to back down. The guy is bleeding on the floor of William's room, and she takes him by the shirt to shout questions in his face. When Doggett tries to use the phone to call 911, he becomes the target of her wrath. Mama Bear indeed.