In one of the weirder cases of this trope, Marshall Lee is this to Marceline, being a gender swapped Author Avatar of her. He's a much darker and crueler reflection of her, and Marcy almost seems to wish she could be like him. That said, for a Shadow Archetype, Marshall sure seems to hate seeing Fionna cry.
It's eventually revealed that the Lich and Finn are counterparts: the Lich was born from the Green Catalyst Comet that struck Earth and killed off the dinosaurs and seems to represent Mass Extinction while Finn is the Reincarnation of the Blue Catalyst Comet, which incarnated as a butterfly (a symbol of rebirth).
Aladdin: The Series gives us Mozenrath to Aladdin. Both of them are very clever and quick-witted, yet they are occasionally prone to letting their youthful impatience and boredom get in their way of completely reaching their fullpotential, and they're both hinted to have rather unpleasant pasts. Oh, and neither of them is ever seen without their faithful animal companions.
All Hail King Julien features the evil Fanaloka Karl who explicitly declares himself to be in a battle of light and dark with King Julien, and he's not too far off; both are eccentric and have huge egos and both make their Home Base in the ruins of a crashed human aircraft.
In Avatar: The Last Airbender, there are numerous parallels between Katara and Azula: roughly the same age, they are both the daughters of leaders with leadership skills of their own, both freakishly powerful and talented prodigies with their elements, both at least occasionally overbearing control freaks and possessed of a dangerous temper when provoked. On opposite lines of the Red Oni, Blue Oni divide they may be, but taking into account their fathers' personalities/influences they are far more alike than one may think.
Azula also serves as an Evil Counterpart to both Zuko and Iroh. As Zuko's, she shows what he could have been if he really did have everything he thinks that he wants (and 50 extra I.Q. points, at least). As Iroh's, she tries to steer Zuko down the wrong path rather than the right one. This is lampshaded in a dream sequence Zuko has, in which he is being consulted by a red dragon and a blue dragon on which path to take in life, good or evil. The red dragon, who advocates good, has Iroh's voice, while the blue, who advocates evil, has Azula's. This situation comes true in Book 2's finale, in which Zuko chooses Azula's way only to regret it.
Zuko has another one in Zhao who is older than him, experienced in war, willing to sacrifice others to further his own career, and seems to have favor within the Fire Nation helping him go through the ranks. It is also shown with the fact that they're also unfriendly rivals in the show always fighting whether physically or over Aang. They also attempt to capture Aang for different reasons, Zuko so he can restore his honor and return home, and Zhao as a vanity project.
Hama serves as another Evil Counterpart to Katara. Both of them went through horrible things during the war against the Fire Nation (Katara lost her mother; Hama was captured and left to rot in a prison cell); however, Hama became so obsessed with revenge that she became no better than those who hurt her, even going as far as imprisoning innocent civilians in a cave simply because they were Fire Nation.
In Batman: The Animated Series, The Creeper was presented as the Joker's good counterpart, being doused by the Joker's Psycho Serum but turning out as a well-intentioned mad man. Amusingly, he is just as obsessively attracted to Harley Quinn as she is to the Joker. It also puts the lie into any idea that the Joker's origin makes a Freudian Excuse: the same thing happened to another man, but while he became just as delightfully insane, he doesn't go around killing people.
Roland Daggett is one to Bruce Wayne, an evil man who uses his wealth to achieve ends with very destructive means vs. a responsible billionaire who uses his wealth to improve lives and risks his life to defeat criminals.
In a rare villain to villain example, Grant Walker to Mr. Freeze. As pointed out by a reviewer for the episode Deep Freeze, Mr. Freeze is man who claims to be dead to emotions, but whose emotions - mainly his love for his wife- drive his actions, and what prevent him from carrying out Walker's plan, not to mention hating his frozen state. Walker is a seemingly kind man, who thinks nothing of freezing all but a select few to create his own world, and who prefers the confinement of Mr. Freeze. This made him more of a Mr. Freeze than the original one.
Kevin, aka "Kevin 11" from Ben 10. Only a little in his first appearance, but more and more each time he shows up. He starts as a sociopathic kid a little older than Ben with the ability to absorb energy. He absorbs energy from the Omnitrix twice in his debut episode, each time transforming him halfway into one of Ben's alien forms. By the time he resurfaces in his second episode, he's all alien, and can change between them, but can't stay human very long. At the end of that episode, he winds up as a freaky hybrid, incorporating a little bit of human form and aspects of all 10 original aliens, and from then on he's stuck that way.
Gwen also became a Good Counterpart to Charmcaster after stealing her spellbook and using it to learn magic.
In Alien Force, Kevin pulls a Heel–Face Turn and gets his own Evil Counterpart as a result, Mike Morningstar/Darkstar, who also has energy absorption powers. Ben, in the meantime, gets a new Evil Counterpart in Albedo, who doubles as his Evil Twin.
Omniverse has Khyber's alien dog Zed who can transform into monstrous predators with the aid of the Nemetrix, a technology-based example of this trope to Ben's Omnitrix.
Dr. Psychobos, the creator of the Nemetrix, acts as this to Azmuth, convinced that his race, the Cerebrocrustaceans, are intellectually superior to the Galvans.
Captain Planet has an evil counterpart in Captain Pollution, composed of the polluting powers of Super Radiation, Deforestation, Smog, Toxics and Hate.
Zarm is to Gaia.
The ChalkZone episode "Reggie the Red" had Reggie Bullnerd find a piece of red chalk and end up in ChalkZone. Until the red chalk is eliminated, Reggie becomes an evil counterpart to series protagonist Rudy Tabootie by using the red chalk to cause misery and destruction when Rudy would use his magic chalk to instead solve the problems of the denizens of ChalkZone and save them from whatever threatens them.
Dan Vs.: In an inversion of this trope, Elise can be seen as a Good Counterpart to the Villain Protagonist, Dan. Both are snarky, cynical, deceptiveDeterminators from abusive families who are so vindictive that they can (and do) go to Ax-Crazy lengths to seek revenge on whatever has wronged them. In addition, both are associated with Chris to the extent that they serve as Vitriolic Best Buds to him. Elise has admitted that she actually enjoys some of Dan's revenge schemes. She even does the Skyward Scream whenever something angers her, and in one episode literally participates in Dan's opening scream. The difference is that Dan is a misanthropic Anti-Role Model who can sometimes be a source of Nightmare Fuel, whereas Elise is the sanest of the three. Regarding Chris, Dan emphasizes the abuse while Elise emphasizes the caring.
Vlad to Danny in Danny Phantom. True to the trope, the Not So Different speech is one of Vlad's favourite tactics, leading to the expected denial from Danny.
Negaduck -both versions, the first arguably moreso, as he is the the dark half of Darkwing's personality, given form after he is zapped by Megavolt's Tron Splitter device. He resolves to kill his Posiduck counterpart, so as to conquer the underworld undeterred. The second, from a Mirror Universe, is no less evil, as he delights in the thought of murder, and at one point tries to destroy all of St. Canard in one fell swoop.
There is another evil counterpart of Darkwing known as Darkwarrior Duck from a Bad Future. Gosalyn disappears when she accidentally hitches a ride with the time travel device that took her to Darkwarrior's time. The loss broke him so much that Darkwing started to take a much more hardline stance towards fighting criminals, running all of them out of town before turning Saint Canard into a full-fledged Police State where All Crimes Are Equal.
Dinotrux has Ty Rux and his friend Revvit, to D-Structs and his servant Skrap-It.
In Dragons: Riders of Berk Hiccup is given one in the form of Egomaniac Hunter and leader of the Berserker tribe Dagur the Deranged. Where Hiccup wants to befriend dragons, Dagur starts out wanting to simply hunt them before deciding he wants to use their power for himself and has his sights set on taking Toothless from Hiccup. Dagur's status as Hiccup's opposite is confirmed in "A View to a Skrill, Part 2" when he forces the captured Skrill to attack Alvin the Treacherous against its will.
The Dreamstone utilizes a non character example, instead one of the title MacGuffin. The Nightmare Stone, much like the Dreamstone is Exactly What It Says on the Tin, a magical gem able to send nightmares to sleeping residents while fending off good dreams. In another reversal, the heroes are made to steal the Nightmare Stone from the villains much like the latter try to steal the Dreamstone throughout the series.
For a character-based example Zordrak may be this to the Dream Maker, an intelligent and highly powerful sorcerer who uses his power to send dreams to the world around him and watches over a population of somewhat loyal bumbling creatures. In contrast to the benevolent Dream Maker however, Zordrak is a Bad Boss vehement on conquest and spreading nightmares.
On The Fairly OddParents, Timmy might have three: Remy Buxaplenty, Mr. Crocker, and his imaginary friend Gary. Remy is a rich kid with a fairy godparent and Crocker had fairies (Cosmo and Wanda) until Timmy caused them to be revealed when he went back in time. Timmy has had Not So Different moments with Remy and Crocker before. Gary is a stereotypical cool kid similar in build to Timmy, who can also make Cosmo and Wanda grant wishes for him due to originating from Timmy's psyche.
Subverted in an episode of Foster's Home for Imaginary Friends, where Mac's Big Brother Bully Terrence attempts to make his own imaginary friend to deal with Bloo, who constantly manages to humiliate and outsmart him whenever he starts picking on Mac. Not only is he square in contrast to Bloo's round, blob like appearance, he's red and, surprisingly, named Red. It's Subverted though in that, despite being made to be an Evil Counterpart to take on Bloo, Bloo easily outsmarts and humiliates him at every turn, and once he begins to realize Red isn't that bad a guy after he pushes his pranking too far, offers to be friends with him. Red quickly realizes that Good Feels Good and starts going after Terrence for picking on Mac. All in all, he's arguably a nicer imaginary friend than Bloo himself!
In Futurama, Fry assumes that the character Flexo is this to Bender but his jealousy blinds him to the fact that it's actually the other way around.
Fry: How can I live my life if I can't even tell good from evil?
Thailog of Gargoyles is an Evil Counterpart to both GoliathandXanatos, ironically enough. He's Goliath's evil clone, but he also embodies the depths of evil of which Xanatos would become capable if he lost the last threads holding him to his humanity. Both characters see Thailog as one of their most dangerous enemies, if not the most.
Gravity Falls has Gideon to both Dipper and Stan; he has knowledge of the supernatural and a desire to unlock the secrets of the town comparable to Dipper, and he and Stan are both con men while both also having links to the genuine paranormal, but where Stan is a Jerk with a Heart of Gold Gideon is a straight up psychopathic Corrupt Hick.
The 2015 Inspector Gadget cartoon has a new character named Talon, who is an evil counterpart to Penny. Penny is a very intelligent girl who aids her Uncle Gadget while Talon is the nephew of Dr. Claw and uses his genius to help his evil uncle in his schemes.
Deirdre to Rebecca. Rebecca is a maiden and Deirdre is a crone, they are both wise in the ways of medicines, potions and the like with Deirdre being wise when it comes to the occult and both are presumably the only non-Saxon/Norman of their group. Rebecca, while never stated, is Jewish and Deirdre, if her name is any indication but considering Gawain is a Saxon she might not be, is Celtic.
Prince John is also one to King Richard, no better shown than in "A Friend in Need" where a peasant says that there were "fewer taxes under good King Richard."
Daolon Wong: It would appear you are the appropriate Yin to my Yang, good wizard.
Hak Foo to Tohru after the latter reforms. Even in Hak Foo's debut episode, in which Tohru is still a Dark Hand Enforcer, the hammy master martial artist is presented as a more brutal and less intelligent version of the reserved sumo.
If Jade has any Evil Counterpart, it would be Drago. They're both the youngest members of their respective sides who might seem at first glance the most harmless ones. They're reckless, sharp-tongued and rebellious, yet also more flexible thinkers than their elders. They have potential in a variety of skills (like martial arts, stealth, magic and leadership), and despite their rebelliousness, they want their achievements to be acknowledged by their elders (namely Jackie and Shendu).
On Kim Possible, Dr. Drakken's Dragon Shego is a sort of evil counterpart to Kim. She's a former teen hero herself. The similarities in their overall character design leads some new viewers to think Shego is Kim's Evil Twin.
They also both get together with their partner in crime/justice. There is an episode dedicated to just how similar they are if Shego was good; they are so compatible it ramps up the Ho Yay to very impressive levels for a Disney Cartoon, due to it splitting up the Kim Possible + Ron Stoppable romance.
Though he's considered Kim's archenemy, Dr. Drakken serves as an evil counterpoint to Kim's sidekick Ron. Both are not particularly good fighters and leave fighting to their female companions. Drakken is outwardly intelligent, but manages to botch many of his schemes due to incompetence. Ron often acts buffoonish, but it's implied that he holds some innate intelligence. Their similarities are highlighted in the episode "Bad Boy".
In The Legend of Korra the titular protagonist is pitted against various antagonists that reflect her in some fashion.
Amon initially represents the idea of an ordinary human born without bending, but later gaining power from the spirits in order to take away others bending. Contrasting each Avatar's reincarnation and multiple bending abilities being the result of a permanent fusion with a spirit.
Unalaq literally becomes Korra's evil counterpart by fusing with the spirit that embodies the polar opposite of the one empowering the Avatar.
the final Arc Villain of the series, Kuvira. Both are about the same height, build, and personality to make it seem like Korra is attempting to "overcome a past version of herself".
Baatar Jr. serves as this to Asami; both betrayed their families over ideological differences, both are skilled engineers and pilots, and both, non-benders and both are the love interest of a powerful bender who is trying to bring Balance/Order to the world. However, where Asami is often shown as being kind and selfless, Baatar Jr. is shown to be rather self centered and far more violent.
Though he is much younger Zaheer is the counterpart to Tenzin. Both are skilled Airbenders with similar ideology and both, (in a way), are mentors to Korra.
Men in Black: The Animated Series: The Fmek alien race is the Evil Counterpart to the Arquillian alien race.
In Metajets, The Stunt-Hawks are a trio of criminals flying newer, more advanced transforming jets designed by the same man who designed the good Metajets.
Tooley to Texas in Motorcity. "Threat Level: Texas!" has the two of them interacting for most of the episode('s real time). Kaia is this to Mike, as they both want to stop Kane, but Kaia is willing to harm innocent people in the process. During the Mushroom Samba of "Mayhem Night" Mike sees a literal evil-version of himself, possibly as a reminder of his past working for Kane.
In season 4, there's Suri Polomare, an evil counterpart to Rarity. Both wish to make a name for themselves in the world of fashion, but while Rarity is known for her generosity, Suri is selfish and manipulative. She sucks up to Rarity just long enough to take advantage of her generosity, and is more than willing to lie, cheat, and steal in pursuit of fame.
My Little Pony: Equestria Girls gives us Sunset Shimmer, a former student of Princess Celestia. Unlike Trixie, Sunset is actually a perfect counterpart to Twilight as Sunset couldn't give two flips about studying, believed herself to be superior, would go so far as to use underhanded tricks to shatter friendships and ruin other people's fun for her own sake. Oh, and turning into a friggin' demon might have a factor in this.
Ironically, in My Little Pony: Equestria Girls – Rainbow Rocks, Sunset herself would gain one after changing her ways, in the form of Adagio Dazzle. Adagio is basically every bit as selfish, cruel, and power-hungry as Sunset was, only she has none of the few redeeming traits Sunset had, and the talent to be a threat rather than the local high school bully.
In My Little Pony: Equestria Girls – Friendship Games, Twilight's human Alternate Self, mentioned in the first film and seen in The Stinger of Rainbow Rocks, is a member of the Crystal Prep Shadowcolts, the rival team of the Canterlot Wondercolts. Naturally, she winds up coming into conflict with Sunset, and their final confrontation is heavily reminiscent of the one from the first movie, but with the places reversed.
Twilight gains another one in season 5 named Starlight Glimmer. Both seek to spread friendship across the land, but Twilight offers genuine friendship while Starlight offers a false one through brainwashing. Twilight studies and trains to overcome her limitations and encourages others to do their best, while Starlight became bitterly jealous of others and so found a spell that can take away the talents of others, so nopony can ever be better than her. While Twilight became a new Princess of Friendship in Equestria, Starlight became a sociopathic dictator in a False Utopia town, with aspirations to take her message outside of her town. It also reflects in their backstories. Twilight has had friends, social status, and guidance since youth and had the benefit of being under the tutelege of Princess Celestia, Starlight has had no such fortune, having suffered a broken friendship and having pretty much spent most of her life alone, which led to her status. It's even lampshaded when the two meet, as Starlight becomes increasingly jealous and resentful of Twilight's talent and fortune, to the point where Starlight develops a personal vendetta against her that grew even stronger after the season 5 premiere.
In an episode of Phineas and Ferb, the titular boys compete with a pair of similar kids named Thaddeus and Thor. They're not evil, per se, but Thaddeus is obviously a Jerkass compared to Phineas. They're also a little inferior to them, however.
In the episode sequel, the same can be said for Doof-2's wife Charlene-2, who is as evil as him (as opposed to the original Charlene, who believes that no one can be evil in real life), and their daughter Vanessa-2 (as opposed to the original Vanessa, who lacks any interest in doing evil).
The Powerpuff Girls has two sets. The Rowdyruff Boys are a group of little boys with the same powers but the opposite morality, and were created by Mojo Jojo from snips, snails, and puppy dogs tails. The Powerpunk Girls (Berserk, Brat, and Brute) are from an alternate universe where the evil Oppressor Plutonium (Professor Utonium's own Evil Counterpart) created them out of salt, vinegar, and everything nasty (and Chemical X) to conquer the world. (Although in the case of Buttercup and Brute, the only real difference between their personalities is that Brute's tendency towards violence is amplified.) Mojo Jojo has a Good Counterpart in this reality who is a hero.
Dick Hardly is one for Professor Utonium, being little more than a sleazy money-grubbing scientist who made knockoffs of the Powerpuff Girls with no legitimate love for them.
The Real Ghostbusters had to deal from time to time with the "People-Busters," their Spirit World counterparts (a similar concept also featured in Tokyopop's Ghost Busted anthology manga). They also dealt with "ecto-clones" of themselves, which manifested when a crack in the Containment Unit bathed their ectoplasmically-saturated original flightsuits in PK energy.
Robot Chicken had a sketch revealing a "Negative Wonder Woman". The most evil thing she does in the sketch involves merely robbing a bank, but she does make herself known to act cruder than the real Wonder Woman. As for costume, since Wonder Woman's leotard leaves her arms and legs exposed, but covers up certain feminine parts, Negative Wonder Woman wears an outfit that covers up her arms and legs, but leaves those feminine parts exposed.
In an episode of Sam & Max: Freelance Police, the eponymous duo accidentally release Dangly Deever, a Howdy Doody-style children's show marionette, while futzing with one of the Geek's numerous research projects. This seems harmless enough, until the Geek returns in time for an evil version of Dangly, and several other puppets who didn't get good counterparts, to break free. At the climax, the two Danglies are struggling for dominance while the heroes try to pick out their target.
The episode "Jack versus Mad Jack" of Samurai Jack deals with Jack's inner rage building to a peak when he gets bombarded by nearly a dozen bounty hunters. Aku, watching Jack's anger boil, sees that his fury is powerful in its own right and decides to manifest an evil duplicate called Mad Jack to turn it against him. However, Jack soon discovers that Mad Jack's existence is tied to the rage that currently resides in him, so Jack takes a second to cool his head and purge his mind of that rage, which wipes Mad Jack from existence.
Scooby-Doo! Mystery Incorporated posits that there was a group of teen mystery busters before Scooby and his crew (also called Mystery Inc.), and their team mascot was a parrot named Professor Pericles. When the Gang learned that Conquistadors left a treasure in their hometown of Crystal Cove and clues to finding it, Pericles became corrupted and struck a deal with a team member, only to be double-crossed and committed to an asylum. In contrast to Scooby—a dimwitted but lovable animal companion known for his unfailing loyalty—Pericles is frighteningly intelligent, but also entirely amoral, and he's more than willing to stab his friends in the back to make his visions come true.
The Posthumous Character Abigail Gluck is framed as an Evil Counterpart to Velma, taking her famous intelligence and social awkwardness to chilling levels. She served as The Smart Girl of the Benevolent Lodge of Mystery in the 1880's, but was apparently just as amoral as Professor Pericles, devoting her scientific acumen to building deadly weapons of war in her old age—and she may well have been involved with the Nazis at one point. note This being a kid's show, no one ever actually says "Nazis". But she's outright said to have built robotic soldiers in the 1930's, her robots wear World War II-era German helmets, and they all have German names. Do the math. She apparently served as an Evil Mentor to Pericles, and eventually secluded herself in an underwater base that she built herself, where she eventually died of old age—alone and unmourned.
This trope was inverted and played straight in one episode of Sonic Underground. When the protagonists visited a Mirror Universe, their own counterparts were evil, tyrannical rulers, while a good Robotnik was the leader of the Resistance.
From The Simpsons, Maggie Simpson had her arch-nemesis Gerald the unibrow baby.
Watch the episodes with Sideshow Bob and you'll realize he and Bart are more alike than either would care to admit. They're both manipulative, clever, and quite self-centered. The difference is that Bart is a nice person deep down and shows genuine remorse for his actions (when they go wrong), whilst Sideshow Bob only cares about accomplishing his goals and eliminates anyone who gets in his way.
Jessica Lovejoy is also one to Bart. While Bart is openly a troublemaker, he also has moments of sympathy and morality. Jessica, however, hides behind an image of being the pure-hearted Reverend's daughter, while acting in ways that horrify even Bart.
Asajj Ventress is this to Anakin. They both used to be slaves on a remote Crapsack World, have been rescued by a Jedi, who were considered somewhat "rogues" by others, both of their rescuers died, and both of them became the apprentices of a Sith Lord. Interesting to note, that while Anakin started slipping closer and closer to the Dark Side in Season 4, she seems to have started to work on a Heel–Face Turn at the end of the same season.
To a lesser extent, Ventress is a counterpart to Ahsoka as well: both of their masters were Jedi who fell to Dark Side, both of them strove to prove themselves worthy of their respective masters, they both started by using a single green-bladed ligthsaber, and picked up Dual Wielding later, and finally the way the Jedi Council abandoned Ahsoka under pressure from the Senate, eerily resembles to how Dooku betrayed Ventress on Sidious's order. They have even come to realize that they have a lot in common.
The Daughter and the Son are respectively the embodiments of the Light, and The Dark Sides of the Force.
In Steven Universe, Jasper to Amethyst. Both are hot-blooded, rude, brash, rely on brute strength, and love to fight. But while Amethyst loves to goof off and has love and compassion for others, Jasper exists to fight, is always serious, and doesn't get the importance of love. She also shares Amethyst's hair style and is physically similar to her, but larger, and they both attack with a spin dash. To further push the matter, Jasper is colored orange, complementary to Amethyst's purple. "Too Far" reveals that Amethyst is a Quartz Gem like Jasper, with Jasper representing what a successful Kindergarten Gem should look like. By contrast, Amethyst is an "overcooked runt" that stayed in the ground too long, hence her short stature and comparatively weaker abilities. This comes to a head in "Crack the Whip", where they finally fight. Jasper, thanks to a combination of training and her superior capabilities, beats her down easily. "Beta" takes this even further by revealing that Jasper was also made on Earth, in the Beta Kindergarten. All the other holes are misshapen while hers is the only one that's perfect. And while Amethyst sees Jasper as her Arch-Enemy, Jasper views her as an embarrassment.
Word of God says they designed Slade to be an evil version of Batman, though Batman himself never appears in the series (except possibly once, in silhouette).
From a team standpoint, the HIVE are the evil counterparts to the Titans, at least before they became Flanderized into joke villains. Brother Blood doesn't start out as an Evil Counterpart to his Arch-Enemy Cyborg, but becomes such during the events of the third season finale.
Lotor's Robeast in Voltron: The Fleet of Doom is an Evil Counterpart to Lion Voltron and Vehicle Voltron.
Dracotron in Voltron: The Third Dimension, which is made up of 5 robot dragons, is an Evil Counterpart of Voltron.