The Epic of Gilgamesh makes this trope Older Than Dirt. Gilgamesh is hot-headed and arrogant, and uses his status as god-king to always get his way, (especially with the young brides) so in response to the people's prayers expressing annoyance with Gilgamesh, the gods create Enkidu, a wild beast-man who is tamed via The Oldest Profession and becomes the only person who can rival Gilgamesh's strength, thus holding him accountable fot his actions. Whereas Gilgamesh is bold, arrogant, and hasty, Enkidu is level-headed and expresses understandable fear at the things Gilgamesh wants to do.
Played for Drama in A Prayer for Owen Meany. The titular character, while physically weaker than the narrator, is self-driven, determined, assertive, and has a good head on his shoulders, if not a bit bullheaded. In stark contrast, Johnny is passive, unmotivated, socially off, maladjusted and after Owen's death, utterly lost and stuck in a rut.
In Animorphs, it's all over the goddamn place. All the main characters act as foils to each other to some extent.
Marco is foil to Jake (taking orders vs. giving orders), Tobias (pragmatism vs. idealism), Cassie (pragmatism vs. moral relativism) and Rachel (subtlety vs. brute force).
Jake is foil to Marco (taking orders vs. giving orders), Rachel (leadership vs. insubordination; they say this is what happens when two "strong" personalities mix), Tobias (confidence vs. insecurity) and Ax (leadership vs. loyalty to authority figures).
Cassie is foil to Marco (pragmatism vs. moral relativism) and Rachel (peace vs. conflict).
Tobias is foil to Rachel (peace vs. conflict), Jake (confidence vs. insecurity), and Marco (pragmatism vs. honor).
Rachel is foil to Marco (subtlety vs. brute force), Jake (leadership vs. insubordination), Cassie (peace vs. conflict), Tobias (peace vs. conflict) and Ax (giving orders vs. taking orders).
Ax is foil to Jake (giving orders vs. taking orders), Marco (pragmatism vs. "warrior ethics"), and Rachel (emotionality vs. logic).
Ellimist and Crayak act as foils to each other (life vs. death, the forces of good vs. the forces of evil).
Visser Three is foil to Visser One (psychopathic, sadistic, irrational evil vs. pragmatic, intelligent, everyday evil).
Visser Three is a foil to Alloran. Visser Three declared his brother a traitor and was responsible for him being forced into hiding, whereas Alloran's brother was the one with the goal of killing Alloran.
In The Lord of the Rings, Boromir might be considered the foil to his brother Faramir as well as to Aragorn, as while he had similar heroic goals, he is a Tragic Hero who is tempted by the Ring.
Saruman and Gandalf are both powerful wizards, however, Saruman is seduced by power, whereas Gandalf refuses to take the Ring.
Denethor and Théoden are both the rulers of their countries who succumb to the influence of Sauron and Saruman respectively (Denethor via the Palantír, and Théoden through the influence of Wormtongue.) Both kings also struggle with despair, having lost their son. Ultimately, Denethor succumbs to despair and commits suicide, but Théoden triumphs over it and dies an honorable death in battle.
Denethor and Faramir: both are noble and powerful pure-blooded Númenóreans with the abilities to read the hearts of other men and to command over them, who share a love for ancient lore and other scholarly pursuits over feats of arm. Yet all these similarities only highlight their differences: the son is warm, gentle and understanding where the father is cold, harsh and scornful. Faramir chooses to keep on fighting despite having lost all hope, Denethor succumb to despair. Faramir demonstrates humility and open-mindedness, Denethor displays arrogance and stubbornness, etc...
In The Silmarillion and The Children Of Hurin, Tuor and Túrin might be considered each other's foil. They're cousins (though they -almost- never meet), both their fathers are lost in Nirnaeth Arnoediad, they are separated from their human families to be fostered by Elves, go live in hidden Elven cities, fall in love with Elven ladies... However, Túrin is a rash, not always sympathetic Tragic HeroBlessed with Suck while Tuor is an all out good guy who ends pretty well - what with being one of the few characters who actually survive to the end of the book.
The ValarAule and Melkor/Morgoth serve as foils. They are both Valar who have their own ideas and don't always work with Eru's plans for Arda. However while Aule tried making his own life, creating the Dwarves, he repented of doing so when Eru reprimanded him and Eru gave the Dwarves true life for this. In contrast Melkor 'creates' his own creatures by corrupting Eru's creations, such as the Orcs being made from corrupted Elves. Aule created Dwarves out of a desire to populate the Earth and actually loves his creations as his children. Melkor breaks with Eru's plans out of envy and doesn't love his creations, Tolkien wrote Morgoth would have eventually destroyed them.
Eärendil and Maglor. Both are grandsons of High Kings of Noldor. Eärendil is the genetic father of Elrond and Elros; and he, albeit of son of mortal Tuor, sets sails to West to seek help of Valar to beat Morgoth. Whilst away, the Sons of Fëanor attack Sirion, and whilst Eärendil's wife Elwing escapes with Silmaril, she leaves young Elrond and Elros basically orphaned. Maglor then becomes their foster father. With Silmaril, Eärendil and Elwing eventually arrive to Valinor, and Eärendil chooses the life of Elf (although his heart was more on his father's kindred). He eventually becomes the Lightbearer, sailing forever the vastness of the skies with Silmaril on the mast of his ship, and becomes the sign of hope to Elves and Men. Maglor, on the other hand, eventually gets his hand on the Silmarils, find them burning him because of his (and his brothers') foul deeds, defies the consultation of the archangels of Arda, casts his Silmaril into sea, and is doomed to wander forever the shores of Middle-Earth, singing of pain and regret, never returning amongst the Elven nations, and never even being granted the relief of death like Men. He is presumably still around somewhere...
Sherlock Holmes and Doctor Watson are classic foils. In addition to physical attributes (Holmes tall and lean, Watson shorter and stout), Holmes leaps into plans without explanation and follows up on wild clues. Watson, as his namesake trope points out, tends to ask realistic questions and accept more conventional theories. Holmes is also highly excitable when "the game is afoot" and Watson, a war veteran, is a skilled marksman and cool-headed in combat.
Actually, Watson was never stout in the books — the two times he is described physically, he is "thin as a lathe and brown as a nut" in the first book, and "strongly built, with a square jaw and a thick neck", several years later. This description (plus the mustache) still counts as a physical foil next to Holmes's thinness, pallor, and severe, aquiline features, though. He's also usually portrayed as having brown or blond hair, while Holmes's is black.
Alanna and Kel, the first two female knights in a hundred years. Alanna actively hid and shunned her femininity for years; Kel was proud of her position as the Girl. Alanna is hot-headed and short tempered; Kel is reserved and stoic. Alanna is prone to resenting authority, while Kel is obsessed with duty. Alanna is the prototypical lone hero, while Kell is an effective commander and leader.
George and Jonathon also served as foils to on another, in something resembling Betty and Veronica. Both were natural leaders with devious natures, but George was much more practical and down-to-earth, while Jon was more haughty and big-picture oriented.
Sarai and Dove from the Trickster Duet. Both absolutely hate the treatment of the Raka, but they respond to it in different ways; Sarai rages and rants against it, while the more quiet and sensitive Dove speaks to the people. Eventually Sarai runs away, leading to Dove taking her place as future Queen.
In a Romeo and Juliet story that's way way different from the original, the titular characters are a demon and angel respectively, whose physical appearances(he wore black spiked armor and had black demonic wings to contrast with her white dress and wings and personalities (he was stoic, quiet, and snarky and she was kind, spontaneous, and cheerful) differed. The places they lived in reflected this as well: Juliet's was a peaceful, well-lit, and beautiful realm as opposed to Romeo's gloomy, perilous, and quite frightening one. Despite the current war between the two races, this doesn't stop them from falling in love. Until Paris, Romeo's Evil Twin tricks Juliet into thinking that Romeo killed her father during the last war(which is actually proven to be true) and is just pretending to be in love with her so that he can find out the weaknesses of the Angels and kill her next, putting her in a Heroic BSoD until Romeo tells her that he is deeply in love with her because she is the only one that truly understands him and he proves his love by giving her the necklace her father wanted to give her and he had to kill her father, who was succumbing to fatal injuries that Paris caused. This, combined with Jessica's and Ron's words, makes her eventually forgive him.
Every character in The Stranger is basically a foil for the narrator, Meursault. Not surprising, of course, since the point of the novel is to develop a particular Existentialist philosophy.
In James Swallow's Warhammer 40,000Blood Angels novels Deus Encarmine and Deus Sanguinius, Sachiel is used as a foil to Rafen, for his Pride. At his first appearance, Rafen remembers their rivalry and how Sachiel had always preferred to talk, and Rafen to let his actions speak for themselves. Most starkly contrast when Sachiel thinks Rafen dead (No-one Could Survive That!!) and gloats to the empty air — "Rafen, you are dead." — versus when Rafen sees Sachiel's corpse and feels sorry for him.
In Suzanne Collins's Catching Fire, the reaction of Katniss's family and friends is neatly contrasted with that of her prep team, of whom Katniss observes that they never had to be strong for anyone else. (The District vs. the Capital, in small-scale.)
Later in Mockingjay District 13 acts as one to the Capitol. The Capitol is dependent on the districts, while District 13 is self reliant. The Capitol's people live in luxury, while the people of District 13 have only there basics needs. In the end it is revealed that Alma Coin the leader of District 13 is just as tyrannical as President Snow, the leader of the Capitol, without his redeeming honesty.
Quantum Gravity: The worlds serve as this. Interestingly enough, all of them are foils for all the other ones:
Demons of Demonia are very focused on knowing and being yourself, regardless of what that is, in contrast to the different social rules in all the other realms.
The Fair Folk of Faery, for instance, deliberately hide things from themselves and forget. They are also the strongest aetherically, throwing them that much farther from Otopia.
Elves in Alfheim are masters at hiding themselves, throwing them away from the demons; and also at self-control, in contrast with the generally more playful fey. Their system of alliances would also make anyone from another realm dizzy, and their True Names are very powerful.
Zoomenon is everything broken down into its pure state, meaning the creatures/beings there do not always have what we would call a consciousness, and it is a much harsher environment than anything you'd be likely to find in the other realms outside a volcano or something similar.
But not all men seek rest and peace; some are born with the spirit of the storm in their blood, restless harbingers of violence and bloodshed, knowing no other path. . . .
Ayn Rand loves these, as her characters are archetypes more than they are people. In The Fountainhead, Roark is The Hero and all the others are those who could have been the hero, except for one minor moral failing, or deliberately choosing to be evil, soulmoney-sucking leeches, etc. At least for the men. Women get this treatment, too.
Stolz to Oblomov. The latter is a fat, lazy and pessimistic Cloudcuckoolander; the former is industrious and optimistic.
The earliest example is Rincewind and Twoflower, who react to danger in completely opposite manners.
Granny Weatherwax and Nanny Ogg. Both are powerful, smart, and tough-as-nails Lancre witches. But Nanny is easy going, has a huge family, behaves in a friendly manner, and is usually drunk and telling bawdy jokes. Granny is serious, stoic, never married, feared and respected by all, and has no sense of humor. Naturally they are best friends (and argue a lot).
Vimes and Carrot. Vimes is a cynical, grouchy, dirty-fighting former drunk who has no respect for authority (especially kings). Carrot is an optimistic, ultra-friendly, honorable young officer who always obeys the letter of the law (and may secretly be a king). To make it more complex, Vimes is also clearly a true idealist deep down (his cynicism results from how disappointed he is at the world), while Carrot can show remarkable cunning and deviousness for someone so innocent seeming.
Lord Vetinari and Leonard of Quirm: they're both extremely intelligent, but Leonard is a naive Ditzy Genius who's fascinated with everything, trusts everyone, and doesn't have very good social skills, and Vetinari is uninterested in anything too scientific or technical, trusts almost no one, and can manipulate people into doing just about whatever he wants. There's a bit of a mirror-image quality to their conversations: Vetinari explains whatever devious schemes are on his mind at Leonard without expecting Leonard to understand because he really just wants to talk to himself to get his thoughts in order, and Leonard assumes Vetinari understands all the odd scientific things he's up to even though obscure scientific knowledge isn't exactly Vetinari's forte.
Blair Bissel in Divided in Death is this for Roarke, in that he is not brave, not particularly smart, is greedy, has no conscience, has a fragile ego, and has conquests rather than relationships, unlike Roarke. Eve puts a lampshade on that.
Magdalana in Innocent in Death is this for Eve, in that she is rich, a thief, loves no one but herself, is charming, speaks French and Italian fluently, and will use Roarke to achieve her ends, unlike Eve. Eve makes a comment about Magdalana being the "anti-me".
The Acts of Caine: Berne to Caine. To summarise a lengthy spiel, while both are vicious and skilled fighters, Berne is The Hedonist, while Caine has a cold discipline.
In the Twilight series, there is Bella and Leah. Both are completely and utterly in love with someone (Edward and Sam respectively) and both suffer devastating heartbreak when he leaves them. Bella reacts by going into a Heroic BSoD until Edward returns, abandoning plans of any future or attempts at emotional healing. Leah is forced to move on, fighting to protect Forks and, by Breaking Dawn, planning to deal with her anger issues via yoga and going to a nearby community college. Interestingly, Bella is the hero in this situation, while Leah is meant to be disagreed with.
In Galaxy of Fear the siblings Tash and Zak Arranda gradually differentiate more, with Zak being Book Dumb while Tash is a Bookworm, Zak being more impulsive and physical, and so on. The two Shi'ido scientists, Hoole and Gog, also contrast; Hoole shape-shifts often and takes combat forms but mostly remains in his default form, Gog never fights but is constantly taking forms for The Infiltration to the point where his default form is rarely seen. Hoole also is The Atoner, while Gog... not so much.
Also from Le Mis, Grantaire acts as as foil to Enjolras. Enjolras is a serious man who cares for no one but his revolution, Grantaire is a drunkard and is only in the revolution for Enjolras and cares not for the actual revolution.
In Those That Wake, Mike is one to Mal. Mike is an older man who can't fight for anything because he believes he's worth nothing, while Mal is a young man who fights no matter what because fighting is the only thing that gives him purpose.
In the sequel, Aaron and Rose are foils to Laura. Aaron is a child genius who believes in the good that technology can bring, while Laura is a teenager who doesn't believe technology is good. Rose is clingy and fragile, while Laura is stronger and assertive.
The vikings and blood brothers Hjalmar and Odd in The Saga of Arrow-Odd. Hjalmar became a viking so he will be able to marry princess Ingibjorg back in Sweden, and voluntarily adheres to a chivalrous code of honor. Odd is quite ruthless, fights for his fame only, is not attached to women and plans never to return home.
Isabelle Lightwood is the seasoned, snobbish, girly Nephilim to Clary Fray's naïve idealist tomboy.
Sebastian/Jonathan Morgenstern to Jace: He was experimented on with demon's blood while Jace was experimented on with angel's blood. Valentine raised him to be cold, cruel, and sadistic, while Jace is more compassionate and kind.
Aline Penhallow to Isabelle Lightwood; she's conservative and shy where Isabelle is outspoken and outgoing.
In Vampire Academy, the dhampirs Janine Hathaway and Olena Belikova stand as foils, representing the different life choices presented to dhampir women. Janine chose her career as a guardian over romance and family life. She travels the world with the Moroi family she is sworn to protect. Olena chose to settle down early and devoted herself to raising a family. She has never set foot out her hometown of Baia.
Eric and Four in Divergent. The former preaches all-out combat with no mercy rules, while the latter preaches fair fights with protective rules.
In Gautrek's Saga, King Gautrek is not very bright but very generous; his friend Jarl Neri is clever but a pathological miser.
The Secret Garden: Colin to Mary — both spoiled brats who gradually begin to redeem themselves, Mary faster than Colin. It is through him that the beginnings of her growth are emphasized and encouraged. In fact, to begin with, he's practically her Shadow Archetype.
Frances Hardinge loves this trope, particularly in the Fly By Night Series. The protagonist, Mosca Mye, has a lot of foils - the most obvious are Lady Tamarind and Beamabeth Marlebourne, who are beautiful, graceful and charming rich young women of very high social standing, respected and beloved by everybody. Mosca, on the other hand, is a dirt-poor, "ferret-faced" daughter of an exiled historian, despised and shunned by most. Lady Tamarind turns out to be a religious fundamentalist, which is the furthest thing from Mosca, while Beamabeth is simply an Alpha Bitch with no regard for anyone but herself - Mosca, on the other hand, really does believe in something greater than herself, in spite of her cynicism. There is also a subtler, but interesting dynamic with Mosca and Aramai Goshawk: both have animal themed names, except Mosca's animal is a fly, which is typically seen as a less "noble" animal than, well, a goshawk, neither has a permanent residence. Mosca has a lot of stereotypically male, unladylike attributes (rage-prone, abrasive, loud-mouthed, swears a lot) and wears breeches under her skirt, Goshawk has some feminine attributes, like little delicate white hands and a chatelaine, normally worn by housewives. The colour associated with Mosca is black (the black of her hair and eyes, a fly motif), the colour most associated with Goshawk is, oddly enough, white, even though he does wear all black (the white of his hands, his face and his eyes). Mosca is centered on the accumulation of spiritual wealth - words and books, Goshawk is centered on the accumulation of material wealth. Both set up elaborate schemes, but through completely different means, for completely different ends and from completely different positions.
The whole political and interplanetary conflict is embodied in the characters Frank Chalmers and John Boone. Frank is an unlikable cynic who believes that people are stupid and afraid to make hard choices, forcing people like him to seize control for their own good, and works with Mega Corps to try and minimize their depredations. John is a charismatic idealist who thinks Mars colonization is an opportunity to distill the best qualities of Earth societies and ceate something new and worthwhile, and opposes interference by the Mega Corps as an intrusion of old, stifling systems.
The philosophy of terraforming is argued mainly by Sax, a proponent who wants to turn the planet green, and Ann, who thinks it should be preserved in a pristine state. (They both have Meaningful Names: Saxifrage is a plant known for breaking apart rocks, and Ann's surname is Clayborne.)
In the Unicorns of Balinor series, Ari and Chase (her bonded unicorn) are foils. Chase is a proud, Hot-Blooded warrior who believes he should go out and fight allthe Shifter's minions, right now. Ari is a insecure, cautious girl who often reminds him that they can't serve the rebellion if they get killed. This relationship makes them highly effective on solo missions- even though it sometimes results in mid-battle arguments.
Roland's outward confidence contrasts with Terra's constant internal self doubt. He is also well liked, but ultimately cynical as opposed to Terra who is disliked by others, but ultimately idealistic. Roland's very nature as a liar clashes with Terra's brutal honesty. A big contrast is Roland's innate skill and mastery of the shieldwatch and aeon edged sword, both of which Terra struggles to master through nothing more than hard work.
Hikari is beautiful, skilled, and praised by others, but seems to have suffered from a traumatic past that makes her distance herself from close relationships. Terra's looks are average at best, she has no combat skills at all, and is actively ignored by others, but had a stable home life that provides her with emotional stability.
Delphia is gorgeous and always entering new romantic relationships. Terra is ordinary in appearance and has never experienced a romantic relationship. Delphia is indirect and breaks down into tears with even the slightest hint of a confrontation. Terra is blunt, thrives on confrontation, and never cries.
Kairos was also Alya's squire, just like Terra, but Kairos had an excess of talent and a strong connection with fate unlike Terra who struggled with every aspect of the academy and has no connection with fate at all.
In the Malazan Book of the Fallen, Clip serves as a foil to Nimander Golit. Where Nimander is humble, conflicted and secretly badass, Clip is boisterous and self-confident despite having only a fraction of the skill. They are set in direct contrast to one another where the leadership of their group is concerned.
The Stormlight Archive: Szeth to Kaladin. Both value honor and despise the actual act of killing, and are both slaves after a fashion. In the debate of To Be Lawful or Good, Kaladin falls under "Good", while Szeth ascribes to a version of "Lawful". Whereas Kaladin takesresponsibility foreverything, Szeth takes it fornothing. The powers they exhibit are also similar. However, Szeth is an assassin, not a soldier, and is not actually a surgebinder until joining the Skybreakers, who are rivals to the Windrunners, which Kaladin is one of.
The Machineries of Empire: Kel Cheris and Shuos Jedao. Cheris is a straightforward Kel who's a math prodigy to the point where everyone's surprised she's not a Nirai (of the scientist caste). She's an infantry captain and her signifier, the Ashhawk Sheathed Wings, means she's very stable mentally. By contrast, Jedao is a cunning Shuos, has dyscalculia, has mostly led fleets throughout his career and his signifier, Immolation Fox, is considered an alarm bell by people who know the meaning of it.
Accelerator and Shizuri Mugino have powers that concentrate on destruction while Teitoku Kakine has powers that concentrate on creation. This aspect of their rivalry is actually lampshaded.
Mikoto Misaka and Misaki Shokuhou. Both are Level 5 espers who go to the same prestigious school and are around the same age. Mikoto is good friends with a few people and is a relatively normal and well-adjusted person, while Misaki has an enormous clique (whom she frequently mind-controls) and is extremely paranoid and never trusts anyone. Their powers are starkly different: Mikoto's ability to control electricity is very versatile and makes her especially effective against machines, whereas Misaki's ability to control the human brain is much more limited (including being useless against machines). It's also eventually revealed that they're both in love with Touma, because he saved both of their lives (in separate incidents). However, while Touma and Mikoto interact fairly regularly, Misaki tends to stay out of his life because he can never remember her.
Misaki Shokuhou and Seria Kumokawa. Both are experts in controlling human minds, but Misaki uses her esper ability while Seria manages it entirely through normal techniques. Misaki works for generally selfish reasons, while Seria works for the good of Academy City (by advising one of its directors). And, as with Mikoto and Misaki, they're both in love with Touma.
Motoharu Tsuchimikado and Fran Karasuma. Both are spies sent by the Anglican Church to infiltrate another faction: Academy City for Motoharu and the Kamisato Faction for Fran. Both are knowledgeable about both science and magic. However, while Motoharu became a Wild Card who passes information to both sides, Fran came to genuinely love Kakeru, though she eventually leaves his group of her own will.
In Victoria, Nazi model officer Captain Halsing is this to the protagonist, Marine captain John Rumford. They share a common military background, as well as a philosophical and idealistic temperament, but whereas Rumford is a staunch believer in Christianity, democracy and the American Way, Halsing is equally devoted to Nietzschean philosophy and technocratic Nazism. Also, unlike Rumford, he is well-polished and polite. For Rumford, it is eerie to meet an enemy who is so much like himself, in some ways arguably better than himself, and yet the very embodiment of his own ideological antithesis.
Lux Arcadia and his older brother Fugil. Both are princes to the Old Arcadia Empire, but Lux is the seventh prince (hence last in the line of succession) whereas Fugil is the first prince. Lux is an idealistic hero who tries to save everyone, a concept which Fugil dismisses as foolish and naive. Or rather, that's how Fugil presents himself. It is heavily implied that Fugil is much closer to Lux in personality than is initially apparent.
Lizsharte "Lisha" Atismata and Listelka Rei Arshalia. Both are first princesses of the New Kingdom Atismata and the Holy Arcadia Empirenote This is different from the aforementioned Old Arcadia Empire, respectively. Lisha is inexperienced with politics, isn't afraid to get her hands dirty on the battlefield or as a mechanic of Drag-Rides, and wants to do the best for her people. In contrast, Listelka is a skilful manipulator, doesn't do any fighting personally, and looks down on the common folk. Both of them are in love with the Arcadian princes mentioned above, but in different ways. Lisha and Lux have a relationship of equals and trust each other, while Listelka thinks that Fugil is her loyal and submissive knight when it's obvious to everyone else that he's manipulating her.
Lux and Yoruka Kirihime. Both are royals of fallen countries, but Lux played a pivotal role in overthrowing his while Yoruka worked for the country that destroyed hers (in a failed attempt to prevent it from doing so). Both lacked any rights to the throne, Lux because of being the youngest son and Yoruka because of being a born killer. Both are top-level Drag-Knights, but Lux fights while trying to spare his opponents while Yoruka is an assassin specialised in killing techniques.
Rosa and Hayes both became Ax-Crazy psychos in order to cope with feelings of powerlessness and inferiority. Both were saved by someone (King of Vices for Rosa, Listelka for Hayes) who wanted to use them as disposable pawns while promising them glory. Both went through varying degrees of brainwashing, with Rosa being heavily brainwashed while Hayes received light suggestion and had her personality intact. Finally, Rosa pulls a HeelFace Turn after realizing her master's ideology was just cowardly escapism while Hayes dies unrepentant of her elitist and sadistic lifestyle.
In the battle between the Seven Dragon Paladins and the seven Ragnarok, several of the opposing pairs are foils in terms of powers. Lux (who avoids the enemy's attack and adapts his behaviour to counter them) fights Yggdrasil (which receives the enemy's attack, regenerates and adapts its body to resist further attacks of that kind), Greifer (who can become invincible for brief periods) fights Metatron (which reflects all attacks, except during brief periods of vulnerability), Mel (who can raise and lower temperature) fights Fenrir (which can only lower temperature through its freezing breath), and Rosa (who controls many Drag-Rides that are expendable due to being unmanned) fights Poseidon (which has numerous tentacles that are expendable since it can rapidly regenerate them).
The Forsyte Saga: Young Jolyon and Soames have a first cousin version of Sibling Rivalry and Sibling Yin-Yang going on, so much that they hate each other despite being closely related by blood. Jolyon becomes a rebellious artist with a liberal political mindset, who loves to defy the rules of high society and the traditions of their family. Soames by contrast is an uptight solicitor with a conservative political mindset, who believes that being rich and respectable is the key to success and personal happiness. Of course, things become even worse between them when Soames's wife starts an affair with Jolyon. But they didn't like each other before that happened either.