While Teenage Mutant Ninja Turtles would make use of this trope when it needed to, it was also averted a fair number of times as well in the 2003 series—while the turtles could defeat almost any individual ninja, their most definitive defeats came at times when they were overpowered by sheer numbers. Conversely, the Shredder, proved considerably easier to defeat when he was alone, and did not have his mooks to cover his flanks.
The 2012 series provides a justified progression. The Foot ninja who are trained en masse are outmatched by the Turtles who have been given hands on training by a master for years. However, even the Turtles are outmatched by Karai, who was mentored one on one by another master ninja for a comparable amount of time. It was also subverted once when it was shown that enough Foot ninjas could eventually overwhelm a single turtle with sheer weight of numbers.
Justice League made active use of the trope in its early seasons. The first instance was against the robotic Manhunters and goes as follows: Three Manhunters vs. Justice League. Ends in a tie, but the Manhunters were winning. One of them was not damaged a bit after being hit directly with Hawkgirl's mace. Second encounter: One Thousand Manhunters vs. Justice League. The Justice League tear them apart. Hawkgirl's mace tore through them, as did a green lantern ring. Third Encounter: One Manhunter vs. Green Lantern. The Manhunter overpowered the lantern ring and won.
This trope even occurred in the movie pilot with the Imperium mooks, when first encountered 3 of them go up against Batman and Superman, and they not only hold their own they are barely affected by either heroes attempts to defeat them, but by the end of the movie the entire League is taking out dozens of them, though to be fair at the end the league was taking advantage of their Weaksauce Weakness.
This was solved to a point when the series switched over to Unlimited and the League was given its own personal army. The new team then proceeded to take on fearsome tasks that required multiple individuals, such as when they faced the Dark Heart, a nanotechnology being that could multiply itself exponentially.
This trope is all but referred to by name at one point during the Thanagarian invasion. When she, Superman and Green Lantern are outnumbered by a margin of several hundred, Wonder Woman notes that the final battle features "Pretty bad odds." Superman's reply? "Yeah, they don't stand a chance."
There's Brainiac which kept Superman fully occupied in the episodes he appeared in Superman: The Animated Series. Then came Justice League where Superman, J'onn J'onzz and Hawkgirl are struggling against one to a dozen of Brainiacs. By the end of the episode, J'onn J'onzz, Hawkgirl and Batman can take them out with a single blow.
In Batman Beyond, Terry is investigating someone selling illegal "synthoids." When found out, the guy activates them and sics them on Terry. Terry tears them apart, including one-shotting one modeled after the guy himself, which presumably was made to be a bit tougher since it tried to goad Batman into a fight. Later on, Terry fights a lone one (sold to his friend) that more or less beats him, and is only taken down when it self-destructs out of rage.
In the short to celebrate the Batman franchise's 75th anniversary, an android Batman designed like Bruce in his prime gives Terry hell. Whensevenmoreshowtofinishthe fight, Terry muses that seven against two were pretty bad odds. Bruce Wayne's reply? Snap on an utility belt and declare "For them."
Teen Titans is possibly the crowned king of this trope, providing an on point illustration of it about every other episode using a wide variety of monsters and Mecha-Mooks. Standard example: the villain of the week summons a monster or robot or something. With much struggle and an elongated fight sequence, the Titans are either just barely able to defeat the adversary or make their retreat. Later on in the episode, the villain tries the same trick again, but decides to spice it up a bit by either making the goon 20 times larger or replicating it to form a small army. Despite the blatantly increased odds, the Titans are still able to defeat the both the goons and the Villain of the Week with half the sweat.
Averted by Billy Numerous and Trigon's fire demons. Billy's a formidable opponent (for a Villain of the Week anyway) because of his ability to make hundreds of copies that also have surprisingly good coordination. When Slade leads an army of fire demons to retrieve Raven from Titans Tower, her teammates, despite holding nothing back (Cyborg going so far as to hook himself up to the Tower defense systems to fire dual Sonic BFGs), are overwhelmed by their foes' sheer numbers and Slade's own formidable powers.
Quite possibly the best show of this trope comes from the movie Teen Titans: Trouble in Tokyo. In the intro, the Titans are seen fighting a single colorful villain, who beats them all back with ease and escapes once captured. Mid way through the film they are all attack by one of these while they are separated. At the first part of the final battle, the Big Bad summons a room full of these minions, which the Titans blaze through with little difficulty. Then in the next part of the final battle he summons an army of them, who might as well not even be there at this point as each Titan destroys 3-4 of theme per camera pan. The big difference, of course, is that the Titans has learned that the mooks aren't real or sentient, meaning they're not holding back like they would to capture actual living beings, as Cyborg notes. In fact, if you watch the opening closely, you can see them gradually stepping up the force used. And even with them not holding back, and the Big Bad's imperfect control, they are still overwhelmed.
Another good example of this trope would be the episode "Titans Together", with the victims being the 95% of the Titan's rogues gallery. At first it seemed to be averted when Beast Boy's small team is overpowered by the sheer numbers of the villains. Then this trope was played straight when the other Titans who weren't captured by the Brotherhood reinforce his team (only half of the Titans are in the fight at this point). They then begin picking apart their foes (who had been difficult to beat alone versus the main team) with relative ease despite being outnumbered. Raven even lampshades it.
In an episode of Lilo & Stitch: The Series, the Monster of the Week was able to duplicate anything. However, the qualities of anything it duplicated were divided accordingly (i.e. it could duplicate a 100-watt lightbulb to produce 2 50-watt bulbs). Near the end of the episode, Lilo tricks Gantu into making 100 of each of his combat experiments, making them so weak they're easily defeated.
Adventures of Sonic the Hedgehog has an episode, "Robo Ninjas", in which Dr Robotnik kidnaps a ninja master and brain drains him to teach Scratch And Grounder to be Ninja. After several failures the Nincombots actually beat Sonic and Tails easily. Later Robotnik builds more ninja mooks to defeat the duo and their new ally, but the more Robots he makes the less competent they are.
In Xiaolin Showdown, one of the Shen Gong Wu, the Ring of Nine Dragons, can make duplicates of the user, but the duplicates get less competent the more are made.
Also subverted to great amusement in that Jack Spicer, universal Butt Monkey and self proclaimed 'boy genius,' is actually able to use the ring to great effect, not because he is strong enough that even when divided into nine pieces he is still a formidable opponent, but rather because he's so bad already that the clones couldn't possibly get any worse (though he also may have brainpower to spare).
Played straight in the "Time After Time" with Wuya, Chase Young, hannibal and Master Monk Guan vs Raimundo.
Mala Mala Jong is also able to use it effectively. Considering that he is a demonic living suit of armor where all the part are legendary powerful magical artifacts, it make sense that it can only be worse for the heroes with four of them. They are only able to beat them because they get them into a Xiaolin Showdown where their superior strength provides minimal advantage, and with it won a Wu that forces their obedience.
On Jackie Chan Adventures, whether Jackie had to fight five of the Shadowkhan or five hundred, they would always take exactly the same amount of effort to dispatch.
In the CGI cartoon Roughnecks: Starship Troopers Chronicles, after establishing a base on the jungle world of Tesca Nemerosa, the Roughnecks encounter a 'prototype' Spider Bug that proceeds to kidnap the entire squad one by one with consummate ease, until eventually only two remain uncaptured. When they finally confront it in a suitably epic battle, it takes a barrage of automatic rifle fire and a plummet onto stalagmites to defeat it. Next episode, they're fighting Spider Bugs by the dozens, in combination with the more conventional Bugs, and having little trouble holding their own.
Parodied somewhat in The Fairly OddParents movie "Wishology", in which baby fairy Poof dresses as a ninja and takes out a gang of Eliminators.
An episode of Ben 10: Ultimate Alien had the hero splitting himself into three. The result was superficially successful, but in combat they couldn't coordinate. The hero reversed the duplication, causing the villian to question the wisdom of effectivly reducing his numbers. The single hero, though, easily defeated him.
Even before the combat scene, the duplicates caused problems from their incomplete personalities, though this might have been just poor choices in which personality type to accommodate each task.
Ben 10: Omniverse has a much more ridiculous exemple in episode Special Delivery. Said episode involves one of the biggest Villain Team-Up in the franchise since the Negatve 10. Some of the villains involved include Trumbipulor, who was The Juggernaut in his previous appearance and could give a hard time to Ben even when he was supported by Rook and an entire team of Plumbers, Fisttrick, who could be a relatively good match to Ben in his two previous episodes, and Sunder, who had previously been a match to Ultimate Spider-Monkey, to list only a few. When they all confront Ben alone at the end of the episode, he effortlessly delivers them a Curb-Stomp Battle. Special mention for Trumbipulor, who gets defeated by a form he had previously be shown to be a match to, with a move that originally had no effect on him.
The alien 'Ditto' is almost this entirely.
In Samurai Jack episode 38 there is a textbook picture of the Emperor surrounded by hundreds of Aku mooks.
And for comparison, Jack came close to defeat by a single ninja in episode 40.
In an episode of The Boondocks Bushido Brown is fighting a group of 3 super skilled old people (It's a long story). At first he's kicking all three of their asses; however when he knocks one of them out he starts getting hit and performs poorly.
Averted then played straight on Code Monkeys when Mr. Larrity is jumped by ninjas after Benny, who succeed (at the expense of a few getting killed, but hey) then played straight when the ninjas, revealed as salarymen try to jump him a second time only for him to dodge/kill his way out of the crowd.
Pretty much personified in Hot Wheels Battle Force 5. The show had two Big Bads in the first season, Captain Kalus and Zemerik. Zemerik and his Zurk prefered a Zerg Rush with a massive amount of Sark and The Dragon Zug. On the other hand, Kalus normally went into battle with three other Vandals. The Sark besides Zemerik himself and Zug normally got torn to pieces with ease while the Vandals took a good deal more effort to defeat individually. Then in season two, the new Big Bad Krytus takes control of the Zurk from Zemerik, but has his own group of Red Sentients who are generally far more difficult to defeat than the Zurk are. This comes back to bite Krytus when he faces Kalus' Vandals on their homeworld. Even though there are a lot more Vandals involved, the number wise superor Zurk are ultimately shredded by the Vandals in battle. This is probably justified as the Zurk are mass produced robots with only Zemerik and Zug having any sentient intelligence.
In an early episode of Max Steel, the titular character sneaks in to an enemy base and fights off a couple of mooks, including this scene:
Max: Quality beats quantity. (Five mooks appear in front of him.) I hope.
Naturally, he pummels the mooks and wins the fight...until his arch-nemesis Psycho sneaks up and uses a stun-stick on him.
Transformers Prime: One Insecticon vs. Arcee: Trashed Arcee, Insecticon undamaged. One Insecticon vs. Megatron: Victory by inches to Megatron. Several thousand Insecticons at once, and both of them are one-shotting Insecticons out of the sky. In both one-on-one fights, however, the Insecticon had a home-ground advantage, as well as the advantage of close quarters where guns would be ineffective. Arcee was attempting to distract it so Jack could get to the objective, and Airachnid specifically gummed up Megatron's cannon so he couldn't use it in the fight.
When Arcee fights another Insecticon in "Tunnel Vision" in a subway tunnel, she manages to hold it off by using her greater agility. Yet suddenly even her full barrage can barely scratch its paint. Perhaps it was some sort of close-quarters up-armored variant because of the tunnels.
The show's Insecticons seem to be significantly more vulnerable in their flying form; on the ground their formidable, in the air they get shot down like so many mosquitoes.
The same applies to Vehicons. One Vehicon can be a match for Bulkhead, but a squad of them is cannon fodder. In the pilot, two Vehicons hold their own against Bumblebee and Arcee, only fleeing when Bulkhead arrived. They take no serious damage. Later in the same 5 parter, Team Prime attacks a whole group of them, Arcee is seen effortlessly tearing through them, ripping them apart (literally) effortlessly.
Futurama: in "Benderama", Bender gets his hands on a device that replicates himself. When this becomes a problem, the crew is able to dispatch of the duplicates with as much ease as using a kitchen knife, despite Bender having taken much greater abuse in the past.
In the Hulk And The Agents Of Smash episode "The Collector", on of the Collector's robots takes down Hulk and Spider-man together with relative easy. Later he sends a dozen of them after the whole team, and Red Hulk blasts them all with ease. Justified by being a team of super strong monsters.
Zigzagged in a episode of My Little Pony: Friendship Is Magic. The Mane Six defeat a huge herd of changeling impostors all by themselves, but they can't take on the entire army. Possible Fridge Brilliance: The Changelings are fierce, but Chrysalis claims that she came to Equestria hunting for food for them. They were only weak individually because of malnourishment.