In Agents of the Realm, Norah and Adele. While the former is antisocial and a Jerk with a Heart of Gold, the latter is outgoing, friendly and cheerful once she's past her homesickness.
In Bobwhite, Ivy goes to the library at Redding University (rival to Bobwhite University) and gets annoyed by three guys. Marlene and Cleo realized that these guys are the evil reverse-gender doppelgangers of themselves (though Ivy interjects that her supposed counterpart really looks nothing like her). Which makes things kind of weird when Ivy later starts dating one of these guys (the one who's pretty much a male version of Marlene).
Com'c: Block and Krixwell are contrasts to each others. For example, while Block has yet to even smile in the comic (although he does have a slight smile or three in the December 2013 calendar), Krixwell has yet to say something without smiling.note He does occasionally get the "neutral closed mouth", though.
In The Dreamer, there are several foils: Alexander and Alan, Alan, and Nathan, Beatrice, and Alan, Yvette and Liz, Beatrice and Yvette, Beatrice and Liz, and Ben and Alan.
In Freefall, stretching the long "chapters" to count as sequels, Ames de Morel contrasts Kornada. While Kornada was an idiot attempting to ransack his company's assets, de Morel is trying to implement damaging policies in order to maximize profit.
In Girl Genius, Gil and Tarvek are increasingly making foils of themselves. Tarvek is a well-bred, thoughtful, mannerly aristocrat; Gil is an energetic, sometimes rash, son of a self-risen dictator. They both are in love with Agatha, they're both powerful sparks, and they both want to "ally with" the last Heterodyne and bring peace to Europa — but in different ways. They were also friends at school and now they apparently hate each other.
The main characters, Annie and Kat. Magic Versus Science is a recurring theme of the story and setting, and is represented in the two of them. Annie, who converses with psychopomps and has connections to the ether and the forest, represents the supernatural. Kat, a Gadgeteer Genius who grew up in the Court, represents technology. Personality wise, Kat is more outgoing and interested in pop culture and romance, a stark contrast to Annie, especially at the beginning of the story when she was more stoic. Annie and Kat have both had problems fitting in — Annie because of her personality, lack of social skills, and inability to relate to most people her age, and Kat because of resentment over her grades and suspicion that, as the daughter of two Court teachers, she was being favored. Annie and Kat balancing each other is a recurring theme in the Treatise pictures, where they are also associated with the sun and moon, respectively.
Zimmy and Gamma, "two strange girls", work as a pair of foils to Annie and Kat, the other "strange girls".
Reynardine the fox and Ysengrin the wolf: Rey is trapped in a plush wolf, likes humans, and has become friends with his "master" Annie; Ysengrin willingly asked his master Coyote, who is constantly insulting him and eating his memories for a humanoid exo-skeleton so he can be stronger (ironically Ysengrin hates most humans and his dependance on the armor appears to be atrophying his real body).
Reynardine and Hetty, who despises her "master" and wants to kill him to be free Hetty's "master" is a young boy who has no idea Hetty exists and it's implied Hetty killed his sister, her original master. Rey's real form is a land-dwelling mammal (fox) while Hetty's appears to be a water-dwelling crustacean (shrimp).
Kankri was intended to represent the worst of social justice bloggers (being overly obsessed with details, giving sermons instead of having conversations, being generally arrogant and condescending) and Porrim the best (articulating her point clearly and concisely, sorting through bullshit and real problems, and generally having a life outside social justice).
John and Rose have foils in Tavros and Vriska, who could be described as "John and Rose if they grew up on a dystopian Death World." John and Tavros are both Breath heroes with similarly sweet, naive, trusting, and amiable personalities; Rose and Vriska are both Light heroes who exhibit questionable morality and get played by Doc Scratch even while they're trying to play him.
Jade has Kanaya (both Space players, both had highly unusual guardians, woke up early on Prospit, and have similar theme colors).
Dave and Karkat serve as foils to each other, both being mouthy smart-alecs (in totally differentways) who use snark to cover for their raging inferiority complexes. They're both Knights, have red as their color motif, and even have similar taste in girls (Terezi, Jade).
The B2 kids serve as foils to the B1 kids, especially Dirk/Dave and Roxy/Rose, and the A1 dancestors do the same for the A2 trolls, especially Kankri/Karkat, Latula/Terezi, Aranea/Vriska, and Rufioh/Tavros.
Expanded upon a bit with the B2 kids, who later act like the B1 kids post-Character Development. Roxy is initially a Foil to Rose, though later becomes one to Dave, with Dirk foiling Rose. Jane mostly foils against John — their love of pranks, living up to their past generations, and their happy-go-lucky personalities — with Jake foiling Jade, mostly in their upbringing and whimsical, detachedhammy personalities.
How to be a Werewolf: Marin is a foil to Malaya. While Malaya is terrified and believes being bitten was the worst thing that has ever happened to her, compared to Marin, getting bitten saved her life from a brain tumor and sees it as one of the best things that happened in her life.
In The Indefensible Positions we have Foil (no pun intended) and Frank. It's revealed that Foil was Frank's imaginary friend. After they split up, without him Frank's personality was changed to completely opposite of Foil's.
Lightbringer, a superhero who believes in an objective morality and bent on doing the right thing; and Darkbringer, a supervillain who believes in an objective morality and finds Lightbringer to have misplaced what is right and wrong.
Manly Guys Doing Manly Things: Commander Badass and Tank are foils to each other. Both are burly, blonde and highly masculine super-soldiers, but where the Commander's masculinity is confident and positive, Tank's is insecure and toxic.
Kerri and Terri are foils for each other in Misguided Light. Kerri is the friendly ditz, and Terri is the grouchy one with a brain.
The following quote comes from this strip, featuring Jirix and the Anti-Villain Redcloak talking about their Card-Carrying Villain partner Xykon. Coincidentally, this strip occurs just after several in which the paladin O-Chul and Redcloak had served as different but excellent foils for each other.
Jirix: But... aren't we all on the same side? Redcloak: That is a complicated question... Our alliance with Xykon is one of the most powerful tools we have, and we cannot afford to screw that up. That does NOT mean we should trust him. I know he seems funny and charming, but believe me, when you see for yourself the depths to which he'll sink, you will never sleep well again.
Elan and Nale; polar opposites in Character Alignmentinvoked, both have a flair for the dramatic, similar class abilities (though Nale's Complexity Addiction means he took a more roundabout way of getting them), similar relationships with their respective love interests (who are also foils), and a tendency toward being dumb (though Nale will vehemently deny he is anything but a genius).
Tarquin has several different foils as well.
Elan and Tarquin, who are complete opposites when it comes to alignment (Chaotic Good vs. Lawful Evil) and intelligence. Elan is ditzy, but is intelligent when it comes to narrative trappings while Tarquin is intelligent, but is too short-sighted to see beyond his own narrative.
Tarquin and Julio Scoundrel, Elan's Opposed Mentors. Both are extremelyGenre Savvy, charming father-figures, but one is The Obi-Wan and the other a Darth-Vader-esque Evil Mentor who wants to bend the story to serve his interests.
In the books, The Giant compares him to Miko in terms of narrative role. While Miko has the same ethics the Order has but opposes their goals, Tarquin is (initially) nothing but helpful to the Order despite completely opposing them ethically.
Roy and Thog. Both are melee fighters carrying heavy weapons and both like to talk, but while Thog is a Dumb Muscle and a munchkin-build, Roy is a balanced character: he is pretty smart for a fighter and is a charismatic leader.
It's worth mentioning that Nale deliberately themes his roster around being "Evil Opposites" to his brother's companions, while Roy refuses to accept that Thog is one to him, because that would suggest they're similar in all but a few key ways.
Durkon to Redcloak. They're both devout clerics born to poor families before being forced out of their homes, belong to a species that got the short end of the stick in the OOTS-verse, and are tasked by their gods as the ones to carry out a divine mission that will help their people. But Durkon is honorable and self-sacrificing while Redcloak is a moral coward who is willing to throw his own people under the bus if it'll further his revenge plan. Their fighting styles also differ: Durkon fights on the front lines as a Combat Medic while Redcloak relies on spells and summoning monsters to do his dirty work.
Corrick and Vesper are the most straightforward. One's a Really 700 Years Old badass with supernatural powers, a realistic, if not cynical outlook of life and disdain for his job. The other is an Action Survivor young girl who's slowly growing into a Blood Knight.
Corrick and Azeel: while both are Aurans changed by magic, the former dislikes his gift and aims to protect, while the latter enjoys himself while sowing destruction.
Squid Row: Randie has an organized goal-setting friend who tries to persuade her out of her lack of planning.
Stand Still, Stay Silent: The two non-immune members of the exploration crew, Tuuri and Reynir, are this to each other. They both have a backstory that can be boiled down to Small Town Boredom stemming from the fact that the space between safe settlements is Plague Zombie ridden and only those who are The Immune can move between them freely. Tuuri dealt with it by really wanting to explore non-safe areas and enthusiastically joining an expedition intended to do just that. Reynir, meanwhile, would have been satisfied with seeing a country other than his own and sticking to said country's safe areas. He ended up with the exploration crew by complete accident and is much more cautious about getting infected than Tuuri.
Rachel to The Hero, Bam: Bam is determined to do whatever it takes to do what's right even against impossible odds and succeeds due to hidden powers/luck/destiny, whereas Rachel has none of those three and is just painfully ordinary, and is determined to get ahead at any cost, up to and including morally heinous things.
Hoh to Bam: Appears to be a Nice Guy like him, but (much like Rachel) doesn't have the talent to get ahead like he does, and can't keep up the nice facade in the end. He also brings up how he has lost everything while Bam hasn't. Together with Rachel, they highlight both that not everyone sticks to their morals like Bam, but also that not everyone ever gets the kinds of opportunities he gets to do so.
Hoaqin to Bam: Bam keeps sacrificing himself for everyone, whereas Hoaqin sacrifices everyone else for his own advancement.
Eugene ends up drawing parallels to Bryce, the boy responsible for Gray's friend being hospitalised in middle school. Both start as bespectacled geeks who end up befriending Gray and changing themselves drastically because of it. However, while Eugene learns to be courageous and becomes a steadfast, dependable friend, Bryce instead becomes a jerkass who eventually ends up betraying Gray and Stephen.
Ben (Supporting Leader to the protagonist) and Jake (The Dragon to the main villain Donald) were both powerful but pacifistic boys in middle school who only got involved with the Yeongdeungpo hierarchy for the sake of a loved one (brother for Jake, friends for Ben). In a twist of fate, Jake is even the one to stop Ben getting killed by Donald, as his agreement to join the Union brought Donald away from his fight against Ben. When the two come face-to-face for a long-awaited showdown, Ben realises that they're not so different from each other. Their Animal Motifs (tiger and lion) also play off each other.
of themselves (though Ivy interjects that her supposed counterpart really looks nothing like her). Which makes things kind of weird when Ivy later starts dating one of these guys (the one who's pretty much a male version of Marlene).