Astro Boy is this to Godzilla. The latter was created to express the fear and pain felt by Japanese society after the destruction of Hiroshima and Nagasaki and did it by personifying the idea of nuclear energy into a form of unstoppable monster. The former tried to show the same society the beneficial use of nuclear energy, using a cute, cheerful and heroic nuclear-powered robot protagonist to for that purpose.
Land of the Lustrous: Western (especially, American) readers consider it to be one to Steven Universe. Aside from the Eastern/Western cultural differences, the two went in vastly different directions; whereas the Crystal Gems live on a modern Earth teeming with humans and their presence playing an integral role in the plot, the Gems of Lustrous live on a Earth devoid of humans in the distant future, with their interactions with each other and the Lunarians being the main focus and were in fact evolved from humans. On a more physical level, while both are sexless, the Steven Universe Gems are Hard Light projections of their gemstones that use female pronouns, while the Land of the Lustrous Gems are composed of the minerals themselves and, in the original Japanese, default to male pronouns. "Shattering" a gem in the former will essentially kill them completely, while in the latter they can be repaired with other minerals and strengthened so long as enough pieces are found. Their closest equivalent to "shattering", however, is being ground into moon dust. Unlike Steven Universe, two given gems can't fuse; their memories might, but depending on the will of the gem their personality will swing toward the gem whose parts were augmented into them rather than take on a new personality.
Valvrave the Liberator can be this to Code Geass. The latter has opposing major characters who are too naive and says a wall of lies are needed to make the world gentler. The former is about a machine to "reveal the truth to the world", dealing with characters who are too bitter, and therefore create a safe haven for an oppressed people.
You could also say that Code Geass was also a spiritual antithesis to another Humongous Mecha series from the same director and storyboard artist, Goro Taniguchi, titled GUN×SWORD. Compared to Code Geass, Gun X Sword was a Super RobotSpace Western that took place in a dirty, unsophisticated setting, and featured a main-protagonist that wielded a Whip Sword as well as his own super robot, named Dann of Thursday, to fight on the front-lines. Code Geass, on the other hand, was an Alternate HistoryReal Robot series that took place in a much cleaner, more sophisticated setting, and unlike Gun X Sword's Van, featured a main-protagonist who was more geared toward a strategic leadership position rather than a front-line combat position.
You could most especially see this in the various allied mecha Van and Lelouch had by their side. In Van's case, his allies' Super Robots included a countermeasure against Dann of Thursday and the other Original Seven armors like it, an homage to classic-style Combining Mecha of The '70s, and a rabbit-like mecha designed for tournament combat. Lelouch vi Britannia, on the other hand, had a mass-produced army of Real Robots for both the Black Knightsand, by the end of the series, Britannia itself, with Super Prototypes representing each army including the Gurren Mark-II for the former, and the Lancelot for the latter.
While being a Spiritual Successor to Shakotan Boogie, Wangan Midnight is also this. While sharing both racing themes, Wangan Midnight focuses more on street racing while Shakotan Boogie puts more emphasis on Running Gag and Shakotan-styled cars. Wangan Midnight also took the races on the expressways while Shakotan Boogie focus the races on touge and city streets.
FLCL is another Spiritual Antithesis to Evangelion, also created by the same people — according to rumors, many people who just finished working on End of Evangelion felt down and wanted to create something crazy and optimistic to cheer themselves up.
You may also say that GaoGaiGar, first reconstruction of Super Robot genre after Evangelion was another one of these for it - it celebrated and embraced the same tropes Evangelion criticized or outright rejected.
And GaoGaiGar has its own counterpart in Betterman, a horror/drama show set in the same world.
Voices of a Distant Star and 5 Centimeters per Second - while the former is about love that survives despite great (as in, cosmic) distance between two people, the latter says that not every love can be that strong and sometimes separated people grow apart from each other.
Your Name in turn affirms the views of Voices and Place while rejecting those of Centimeters and Children - even when the universe itself seems bent on separating people and making them forget each other, love will eventually prevail and no barrier is insurmountable - not distance, not time, and not even death.
WataMote could be considered the opposite of The World God Only Knows. In both shows the main characters are big geeks and supremely talented in the field of dating sims and visual novels, but whereas Tomoko is despised for this and desperately seeks love and attention (to a creepy degree), Keima isn't affected by his geekiness and couldn't care less about being popular in real life.
WataMote can also only be one to Lucky Star. Konata is a beautiful Otaku Surrogate girl who is Wrong Genre Savvy, playing life as it if were a dating sim, yet despite this is well liked, very social, and has plenty of friends. Tomoko, meanwhile, is an unattractive girl with greasy, unkept hair, who is very crude and crass. Her social awkwardness, massive ego, and being Wrong Genre Savvy has led to her having only about one real friend. Very much unlike Konata, she constantly seeks attention from the opposite sex, and plays Otome Games rather than Galge. Tomoko is a more realistic depiction of what a female otaku is like rather than idealized surrogate girls like Konata.
The Gundam franchise in general (even the Lighter and Softer entries to a degree) is an antithesis of what Gene Roddenberry's work in Star Trek represented. If there are strange new worlds to see in the Universal Century for instance, expect them to have a lot of the same problems we deal with on Earth.
Another antithesis to Bebop is Space Dandy, made by the same creator. While Bebop is a heavy, realistic look at a 90s cyberpunk future where space travel has only gone so far, Dandy is a call back to Silver age 50s idealistic sci-fi where the possibilities are endless. Bebop focuses on humans and stays mostly on Earth, Dandy has a wide variety of aliens and robots, and doesn't go anywhere near Earth. Bebop has a strong sense of continuity, Dandy's main cast dies in every other episode. Bebop is mostly grays and blues, Dandy is every color it can get it's hands on. If Bebop is Jazz, Dandy is Rock & Roll and Disco.
As part of the science adventure series, Robotics;Notes provides a contrast to both Steins;Gate and Chaos;Head. Setting-wise, the former series takes place on a rural island as opposed the bustling urban areas of the latter two. Thematically speaking, Steins;Gate serves as somewhat a cautionary tale about time travel with the consequences it entails. In contrast, Robotics;Notes takes a more optimistic look at its central innovation (robots in their case) and the potential that can be achieved with them.
Sword Art Online and Log Horizon both involve players in a video game. But while SAO is (initially) The Most Dangerous Video Game, complete with high drama and tragedy, LH deconstructs the trapped-in-a-game scenario as The Game Come to Life, with notable touches where The World Is Just Awesome. Log Horizon pokes fun at SAO's high stakes in its beginning story line. They also have polar opposite main characters, as SAO's Kirito is a black-wearing swordsman who specializes in solo play and surpassing hurdles with his raw skill and experience, while LH's Shiroe is a support spellcaster clad in white, who leads a guild and shines most when it comes to strategy and management.
The problems at the beginning of their respective plots are also opposite: In SAO, drama at first comes from tension; death is likely if you're not careful, and since your real body is comatose and slowly failing, you can also die if you're too careful. In Log Horizon, drama comes from the lack of tension; death is totally impossible, and fulfilling your basic needs is trivial, but you can't enjoy food and you are stuck without a goal. This lead to a lot of characters feeling listless and bored at the start until things got rolling.
Overlord could be seen as another Spiritual Antithesis to Sword Art Online. SAO starts on the opening day of a massively-hyped VRMMORPG, but thousands of players become trapped in the game, and are told by the creator that they can only escape the game by beating the highest level of the dungeon, and if they die in the game, they die in real life. Overlord starts on the last day of a once-popular VRMMORPG that is now shutting down due to its dwindling player base, and only one player gets trapped, without any explanation, in a fantasy world that's highly reminiscent of the game but filled with intelligent, emotional, real people instead of NPCs. In SAO, the teenage main character Kirito starts out at level 1, and spends years in the game, leveling up as part of the player base's ultimate quest to escape the game. In Overlord, the adult main character Momonga has already reached the level 100 cap from years of playing by the time he gets trapped, and he pretty much gives up on escaping on day one, preferring this new fantasy world over the life he left behind, with an unfulfilling job and no close friends or family. Kirito is a hot-headed hero with a strong moral code, reluctant to even kill serial killers in self-defense. Momonga is a cold, calculating strategist with no problem slaughtering entire armies if they get in his way or sacrificing innocent pawns to protect his secrets. At times, the contrasts are so uncanny that it seems like it was done intentionally: Kirito is a dual-wielding swordsman while Momonga is a spellcaster, which seem like total opposites, but when Momonga wants to travel incognito, he passes himself off as a dual-wielding swordsman, something he can do quite effectively with the Super Strength and speed that comes from being level 100, although real warriors recognize that he's just swinging his swords around like an amateur.
Oddly, Macross and its American adaptation Robotech became this as their timelines progressed. In Macross, the Zentraedi become more like humanity, while in Robotech, thanks to repeated invasions, humanity is becoming a warrior race like the Zentraedi.
For most of Space Patrol Luluco, Alpha Omega Nova is a superficially similar but spiritually antithetical version of Kaworu Nagisa from Neon Genesis Evangelion. Both are secretly alien bishonen who use their charm to entice the main character and get closer to their objectives, but while Kaworu is an angel of free will whose love for Shinji is pure and unconditional, Nova has no free will or emotions and merely lets Luluco deceive herself into thinking he could return her love. Yet, in the end, his change of heart makes him a lot more like Kaworu than he was originally.
My Hero Academia is both this and Spiritual Successor for Naruto. On the one hand it happily takes and uses all the tropes and tricks Naruto introduced to battle Shōnen genre. But Naruto is inspired by old Japanese folklore about Ninja, My Hero Academia is inspired by Superhero comics - a quintessentially American thing. Where Naruto was about how a society or a team can work together to achieve what no individual can and how conflicts can tear this apart, Hero Academia is about members of the society polishing their skills to succeed as individuals in a profession where competition is not only unavoidable but even encouraged. Where Naruto was about breaking the cycle of violence and achieving the era of peace, Hero Academia is about living in a world where peace is the status quo while also finding meaning and goals beyond it.
Also one to Marshal Law. Both are superhero works taking place 20 Minutes into the Future that analyze what it means to be a hero. Marshal Law is a Genre Deconstruction with the main theme of the superhero being an unrealistic ideal: the superheroes are portrayed as ineffectual at best and monstrous at worst. Meanwhile, My Hero Academia is very much a Reconstruction. While it has unpleasant and horrible people among the heroes, it ultimately portrays the superheroes as a positive force. Even the main characters are opposites: Marshal Law is a cynical adult who hates all superheroes while Deku is an idealistic kid who idolizes superheroes.
MHA might have one in Black Clover. Both titles are seen as following the footsteps of the Big Three - Naruto, Bleach and One Piece while addressing and trying to improve on the most common criticisms of their formula, like pacing or bloated cast, but, as some argue, the way they go about fixing these issues is fundamentally different. They also differ in their approach to the main character, with MHA having more focus on Deku's Character Development on the road to become a hero, while BC being more about how Asta proves his worth and affects those around him.
Also one to Danganronpa. Both feature schools that have children with incredible abilities, or 'talents' as they are called, and the characters often struggle to find themselves with the enormous pressure that comes with such talents. However, the former is more idealistic then the latter, which has an extremely cynical, Finagle's Law outlook, showcasing what would happen if the academy is corrupt beyond belief. The school puts tremendous pressure on students (who are only there to be studied by a cabal of Mad Scientists), takes advantage of students without talents (through the Reserve Course, wherein their parents pay insane amounts of money to get them entered into a separate, and inferior, branch of the school), and pushes the idea that society only cares about a person's talent and how it can help the world. It gets to the point where the staff try to create a person with every talent available, to act as their messiah in times of trouble, out of someone without said abilities, but also end up killing the subject's emotions. Eventually, all this is exposed to the public, only for the riots to start a chain reaction that leads to The End of the World as We Know It, leading to the surviving students with talents being forced by the new, Dystopian government to play a Deadly Game that is broadcasted to the post-apocalyptic public in order to crush the idea that people, with or without talent, can overcome their despair.
Creator Itosugi Masahiro:
Uwakoi is this for his earlier work Aki Sora, where both series have protagonists who are effeminate Really Gets Around teenage boys and feature many blatant sex with young, pretty girls. Ironically, while the latter deals with forbidden relationship between main characters, it has more chance to achieve happy end than the former. It does so because the latter is played as (mostly) light hearted typical ecchi series and Uwakoi is played for drama and deconstruction of Really Gets Around behavior of its characters.
Inuyashiki compared to Hiroya Oku's most well-known work, Gantz. Both are dark series that don't shy away from scenes of abject human cruelty, but while Gantz revels in its own cynicism, with a clear Humans Are Bastards message and an (initially) utterly unlikable protagonist, the titular Inuyashiki is an All-Loving Hero, with his series having an ultimately more optimistic tone and a message that even the most reprehensible people have a chance at redemption.
Only Sense Online to other works based around virtual reality MMOs such as Sword Art Online. While these other works have the characters get trapped in the game, the titular game of Only Sense Online is just a normal game. It's therefore Lighter and Softer as the players are never in any danger and play the game for fun. Additionally, unlike other works where the main character is a veteran player who's a better fighter than most, the main character of Only Sense Online is a beginner who's comparatively poor at fighting.
Oddly enough, Uzumaki could be considered one to Tengen Toppa Gurren Lagann. Both heavily feature spirals as their central motif, but while in Uzumaki spirals are some kind of nebulous, unavoidable threat and something to be feared, in Gurren Lagann spirals are symbolic of forward progress and human potential. In Uzumaki spirals are terrifying, while in Gurren Lagann spirals are awesome.
The Quintessential Quintuplets: Both sets of siblings are unmistakably unmotivated, but their ways of handling it are remarkably different. Whereas in -San the overly cartoony Matsuno sextuplets had a relatively normal high school life until they burned out in their 20s for whatever reason, the more realistic Nakano quintuplets of Go-Toubun are in their high school years and struggling to pass, with the goal of the series explicitly being preventing them from becoming burnouts in adulthood. Whereas the brothers rely too much on their dependence on others (both to their parents and to each other) and would forcibly maintain the status quo to keep that dependence, the sisters are independent from the get go, with only one (Nino) having the same reasoning as Osomatsu. Also keep in mind that Totoko (their reluctant Childhood Friend) only fell for the sextuplets when they were in their F6 forms, whom all are much more like the Nakanos in concept: friendly, attractive, distinct, and talented, but with their own little problems on the side. Also keep in mind that their love interest, Fuutarou, is willing to take an active interest in getting them to be respectable or at the very least pass high school, while Totoko would rather let them wallow in the same misery she's in.
Shinya! Tensai Bakabon: Both are proported time skips to Fujio Akatzuka's beloved gag manga, being updated humor-wise for adult audiences along the way. Whereas the -San cast was was given new personality quirks and design changes, the Bakabon cast barely aged a day. While the aim of -San was to see how everyone handles in the adult world, Shinya! focuses more on topical humor. One can even see it in they way they handled their respective We're Still Relevant, Dammit! episodes: while the Osomatsu-kun era cast was trying desperately to see what stuck only to come up with nothing, everyone but Papa was content with leaving things the way they were.
Zombie Land Saga to School-Live!: Both are Zombie-flavored mashups with popular female-led genres (Schoolgirl Series for School-Live!, Idol Genre stories for Zombie Land Saga), and they both have a powerful twist to establish the setting: whereas the twist for School-Live! was the fact that the fun times were Yuki's delusion to forget the Zombie Apocalypse, Zombie Land Saga is outright promoted with the apocalypse theme, only for the twist to be that the idols were the zombies rather than survivors. Both do feature a theme of living vs. surviving, but while the School Life Club are trying their best to stay sane without going over the deep end like the Survivalists, the girls of Franchouchou use their new afterlife to do things they never were able to in life instead of hiding away to rot.
Amusingly, this also applies to their dog mascots: while in School-Live! Taromaru is introduced as a loveable companion and dies as soon as he joins the School Life Club, Romero is dead from the start, but still manages to be a good (if not freaky) friend to the group.