While they're beating the crap out of the depowered Mumbo for what he put them through, Jade suggests this approach to Starfire.
Jade herself later performs one of these on the Master of Games when she and Raven are fighting him at the end of the Tournament of Villainesses.
In Shinji and Warhammer 40k, Shinji mentally complains he can't kick Gendo in the teeth because he's too tall, resulting in his mental Farseer giving him some sage advice:
Farseer: How is that a problem? Remember, plan sequentially. Kick him in the shin, first, and when he lifts his leg to rub it, you may punch him in the genitals. THEN when he's kneeling is WHEN you may kick him in the teeth.
In The Bridge, Sonata Dusk manages to defeat a human form Monster X by hitting him in the groin with a fence post. Since he had never been human before, he didn't think to guard it. He staggers around complaining about humans having such a pathetic weak spot.
“Look, if Tzeentch were to actually appear before me after all this in a form with balls to knee instead of some sort of gibbering, tentacled monstrosity capable of driving lesser beings mad with the merest glimpse, then I think it is fair to say that He is asking for the patella to connect with the groin. It will probably even be part of one of His plans, so I honestly won’t feel bad at all,” I explain with bitter annoyance at being underestimated, again.
Tatewaki Kuno: "My name is Upperclassman Kuno. Junior Group E. Captain of the Kendo Club. Undefeated new star of the High School fencing world. But my peers call me… the Blue Thunder of Furinkan High." Ranma Saotome: (...) "I am Saotome Ranma. Heir to the Saotome School of Anything Goes Martial Arts. I invented the Squirrel Maneuver." Tatewaki Kuno: "The what?" Ranma kicks him in the groin.
He's later asked about the name, and explains that it's best summed up as "just go for the nuts".
[James Potter] accidentally kicked Lucius in the balls eight times as he stood up with the man's wand.
In Empire when Snape is teaching Harry etiquette of the wizarding world it's related that the appropriate way of meeting and greeting harpies is to leap around on one leg so that they'll laugh and forget to castrate the male wizard greeting them.
Ladies, and Gentlemen, an INVERSION! The groinsaw from Thirty Hs.
In Lucky Harry freak accidents cause groin injuries to Snape and Draco Malfoy, thanks to Harry's phenomenally good luck.
Harry Crownote by the same author as the aforementioned In This World and the Next and the below-mentioned Souls Abound, making this trope a rather strange Creator Thumbprint of sorts Padma's threat to Neville while they're dancing.
Padma: If your hand goes somewhere inappropriate, my knee will let your groin know.
In Fallout: Equestria, after getting captured by slavers, shortly after leaving her stable, Little Pip muses about bucking one of her captors in the groin, but as she states to herself miserably, they already had her in chains before she could even try.
In the Mind Games arc, Diamond Tiara gets grabbed by a stallion who is heavily implied to be a pedophile. She screams to get everypony's attention, letting them know what the guy is trying, then bucks him in the groin. She runs away and leaves him to be beaten up by the crowd.
Shining Armor receives a pretty brutal one from General-Admiral Makarov (the Big Bad of his arc) during their fight. It involved Makarov's antlers and had enough force to throw him into the air. Fortunately, Shining had armor protecting him, but still took a hard enough hit to disable him for a time and leave bruising. While played for drama at the time (since Makarov IS trying to kill him), the bruising is played for laughs later on, when Minuette is helping a doctor patch him up and seems a little TOO interested in checking the damage.
In a flashback, Shining Armor went on a date with Rising Star. When he gets bored by her story about her ex boyfriend, she throws him across the room, bucks him in the groin, and storms off.
Fluttercruel: Okay, so good news bad news. Bad news, apparently they know about the Stare. Good news is, they're still vulnerable to getting nailed in the stallionhood...and it's still hilarious. (Notices she's being stared at) What? It's important information.
The Cutie Mark Crusaders manage to take out a Changeling by Applebloom bucking his 'apples' then Silver Spoon dropping a very heavy book on his head as he's curled up in agony. Rainbow Dash actually suggests this tactic later.
After being told what the CMC did, Rainbow Dash comments on the number of times she's taken a groin attack over the years of crashing while flying, and warns them that it hurts mares just as much as it hurts stallions. Also, it's noted that due to equine anatomy, the spot is slightly different between males and females.
In Six Brides for Two Sisters, Shining Armor mentions how Cadance has the strength of an earth pony and "shouldn't kick a pony there unless you're absolutely sure," heavily implying this.
Shining Armor can't catch a break and in the Stallions Of Harmony Verse gets one from Rainbow Dash, after tackling her into bushes in an attempt to hide her from Blueblood. The way it looked, she was fully justified in treating him like a molester.
Haku uses one on Naruto in Chasing The Shadow During their first fight scene. Results are... mixed.
In Kitsune no Ken: Fist of the Fox, Suigetsu makes an attempt to hit Naruto in the head with a baseball during their physical education period at school. Naruto's response? He hits Suigetsu's very next pitch back at Suigetsu and straight into his nuts. Cue Share the Male Pain from every guy in the vicinity.
The Child of Love: In chapter 7's omake Asuka kicks the writer’s groin hard after an “It must be that time of the month” comment.
HERZ: Shinji was practicing with his gun as trying to dodge Kurumi's advances. Then Asuka showed up with a sub-machine gun, selected a target at 100 meters, blew off its crotch and head with perfect accuracy, grabbed Shinji and dragged him away.
The One I Love Is: In chapter 7 Asuka was sleeping on her bed when someone fell on top of her. She woke up, and thinking a pervert was attacking her, kneed his groin. Then someone switched the light on and she saw the intruder was Shinji. Oops.
I don't know how she managed, but Asuka ended up on top of me and jammed her fist in my face, followed by her knee in my crotch.
Ritsuko: "I wonder if they even have reproductive organs there?" Misato: "If they do, I'm actually feeling a little sorry for the Angel."
Parodied in "Father Knows Best" -by the author of Nobody Dies and Walking in the Shadow of Dreams-. When Misato hears Shinji screaming, she believes that Asuka has kicked his groin. When she questioned Asuka, though, the redhead replied she never did anything of the sort, and Misato's assumption was dumb.
“So, let me get this straight. You kicked the bed and he screamed because you woke him up and he fell off the bed.” Misato cocks an eyebrow and stares across the kitchen table from Asuka, who has a look of complete innocence on her face. The redhead scoffs, arching her chin. “This isn't a manga. Or at least, that kind of manga.” Misato sips her beer, eyes level on the pilot. In the background, she can hear the shower running. She has a point. If Asuka did kick, with full force, into the most sensitive of sensitives Shinji wouldn't be able to walk, much less run to the bathroom to get ready for school. She's seen the girl kick and there's a good chance she could have kicked it clean off.
In Evangelion 303 Asuka warns Shinji that, if he ever cheats on her, his punishment will involve electricity and testicles.
In A Force of Four, Kara heat-beams U-Ban's groin when he attempts to rape her.
U-Ban was already exposed, about to throw himself upon her. She focused her heat vision on full power and let him have it. "AHHHHHHHHH!" U-Ban screamed, looked very, very surprised, and grabbed his crotch. The very air was steaming around it. Not enough to injure him, probably, but damned well enough to make him hurt. "Pull up your pants," said Kara, getting to her feet. "You look ridiculous."
In Sailor Moon Princess, after a wild party, the girls search through Mamoru's laptop only to find erotic picture of them on there, so when he enters the room, both Rei and Makoto kick Mamoru's groin in anger. However, they later find out that it was really Haruka's laptop.....
In "Tormenting Jean, Killer Robots, and Other Bad Ideas":
Jean: Oh, shit — Scott, I'm so sorry. Don't open your eyes. I'm so sorry. I thought you were Warren. Scott: Obviously. Planning on kicking a certain part of Warren's anatomy, Red? Jean: Something like that.
In "Can't Fight This Feeling":
Hank: But if Scott manages to piss her off too badly, he's on his own. The last time I tried to pull them apart, Jean got in a good kick. That woman is mean. Bobby: I remember that. I think everyone flinched when she landed that kick. Hank: You never have to worry about that happening with two men fighting. We have certain rules of engagement, and kicking below the belt is against the rules. Bobby: She apologized profusely for kicking you. And she bought you a malt later, to make up for it. Hank: I still despair of having children.
Animorphs Redux: When Jake is being strangled by David, who possesses the power to alternately morph multiple different parts of his body, Jake informs David that he bets that David never used all that power to take away his main weakness, subsequently ramming his knee into David's crotch. David tries to regain control of the fight, but is subsequently attacked by new Animorph Melissa in her Doberman morph, with Melisa biting David in the crotch.
Guide Me Home; during a sparring match, Hakoda pins Ursa against a wall and accidentally touches her burn scar. Ursa panics, Groin Attack ensues and Ursa is completely mortified afterwards. Yes, that is an actual tear jerker example of this trope.
"KONO BAKEMONO!" Japan roared. "TO THINK YOU WOULD ACTUALLY TRY TO RAPE ITALIA-KUN!" Punch. Kick. Step on...questionable regions. You would think a male who is only 5'5" would suffer utter defeat against someone who is literally more than a foot above him in height. No such thing here.
In Ah,Nuts!, John and Roy tangle with a druggie who turns violent and directs his anger at John, biting him in the groin. He yelled that he hoped he bit it off, but John escaped with a wound on his thigh and scrotum that Dr. Brackett had to suture at Rampart. He is embarrassed, but Roy reassures him that he really had nothing to be ashamed of, and that the guy was awful for wanting to permanently disfigure him.
In Cub Ron tries to pull ex-girlfriend Hermione into an alcove and when he turns around to talk to Draco Malfoy she kicks Ron in the balls.
In the opening scene of Mirrored, Voldemort demands that Harry kneel before him or he will kill Ron and Hermione. Harry complies but takes this opportunity to punch him in the balls. Ron decides that was the most awesome thing ever (and won't shut up about it) while Hermione cautions that this will no doubt have repercussions seeing as Voldemort was only out to kill him before.
Harry: Hello, Krum. While I know that I'm probably going out of bounds with this, I just wanted to let you know that Hermione is my best mate—she's like a sister to me. So if you hurt her in any way, I'll not only hex your balls off, but I'll also make the rest of your life a living hell. Just so you know—for future reference.
In Souls Abound Millicent Bulstrode kicks her father in the crotch when he tries persuading her to let Voldemort's spirit possess her.
In Unconventional Harry Ginny hits Draco in the crotch with the bag containing Harry's Triwizard Tournament winnings.
This is lampshaded by Deimos's statement: "The final tenet is fight dirty. This isn't a duel nor is it a time to be fair. Gouge your opponent's eyes, gang up on one opponent, use groin attacks, whatever it takes it defeat your opponent."
One chapter has an enemy dinosaur bound to a tree and beaten severely, including several kicks to the groin.
Another chapter has Ducky's mother, armed with twin sticks disable another dinosaur by striking his weapon arm with one stick, tripping him, then kicking him in crotch.
The most brutal groin attack in this story involved a dinosaur kneeing his enemy in the groin, ripping out one of his opponent's eyes, tripping his opponent and almost literally ripping his opponent's head off.
They're reptiles. How does that even work?
Research be damned! It's too much of a good story to let facts get in the way.
In The Legend of Spyro: A New Dawn, Cyros kicks her younger brother Pyros in the groin, then stomps on him there when he says she'll lose a bet, one of her Berserk Buttons. She does it again in the final battle between them to gain the upper hand in their fight.
In particularly graphic example in The Alchemists Heart, after Silver Script and Blossom are attacked and raped by the now male Aqua Regia, who kills the latter Silver Script gets enough second wind to give him an epic No Holds Barred Beat Down where he breaks his horn off, before stabbing him in through the groin with his own horn.
Earlier in the story, while Regia was female (It Makes Sense in Context), she made another attempt to rape Silver Script, that was only stopped, because one of her friends barged in, distracting Regia long enough for Silver to bite her in the clit, which apparently caused enough damage for Regia to limp days after the event.
Later in a more comedic example, while disguised as guard, Silver bucks Blue Blood in the crotch for insulting his late girlfriend.
In The Life and Times of a Winning Pony, this is taken more seriously than most examples when Cloud Kicker delivered a nasty blow to Rainbow Dash's groin, resulting in her nearly bleeding to death. The incident was probably also a major factor in Rainbow Dash's asexuality.
Rainbow receives another painful hit in between her legs in the second story of Ace Combat: Equestria Chronicles. While she is immobilized by Havoc, Trickster takes the opportunity and delivers a painful kick to her groin, causing Rainbow to howl in agony. If he'd done it again, she'd probably had her groin ruptured.
In The Chase is one of the examples where this happens to a female. Berry breaks the 'peace' between House Avarice and Clan Pickled when she justly delivers a beating upon Primrose Propers. She also ensures no more foals will be born to such an undeserving mare.
Another example to female happens in The Dark Side of the Mirror Verse: during the showdown between Mirror Gilda and Mirror Spitfire, Spitfire resorts to bucking Gilda between her hind legs, which stuns her long enough for Spitfire to nearly kill her. Spitfire lampshades the fact most people forget this works on females, and justifies using it herself because Gilda isn't a normal griffin due to a magical accident that pushed all of her abilities to their maximum possible extent. Thankfully, she takes too long to finish Gilda off, allowing her to recover and defeat her.
In the Empath: The Luckiest Smurf novel, Smurfette gives one to Hefty for his saying that Empath couldn't possibly feel a thing for her, with her retort being that Empath would feel more for her in his heart than he would in his private area (insinuating that is how Hefty feels for Smurfette).
Hellsister Trilogy: Satan Girl attempts to knee Supergirl's groin repeatedly as they fight to the death.
Kara drew on her every erg of reserve power to keep fighting. But, increasingly, she found herself on the defensive. She fought to keep Satan Girl's fingers from her eyes, her jaws from her carotid artery, her knees from her crotch.
In Chapter 12 of An Unexpected Child, Bruce actually punches Alice in the dick, causing her to fall over and knock down a pillar, which then falls on part of the circus audience and crushes them to death.