In super robot anime, The Power of Friendship is pretty much one of the main themes, and there are quite a lot of episodes where people turn their backs on the protagonist, but there will ALWAYS be at least one character who will never abandon him.
And that loyalty comes from his loyalty to Marianne. Now that's truly undying.
Guilford is the same towards Cornelia. He's just much quieter about it.
Patrick Colasour embodies this for his superior officer, Kati Mannequin in Gundam 00. The reason is love. The undying loyalty is his cockroach like tendency to survive any dangerous No One Could Survive That situation, especially on her orders. Eventually, it pays off big time with him winning her hand in marriage.
Katekyo Hitman Reborn!: Gokudera towards Tsuna is this trope, completely and totally. Heck, his whole character song seems to be a tribute to his undying loyalty towards Tsuna.
Arguably, Squalo qualifies as this for Xanxus. Not only did he wait 8 years for Xanxus' return, but he grew out his hair and puts up with crap that would make a Bastard Boyfriend seem like a pleasant alternative.
Literally the case of Koinosuke Odago in Jubei-chan, became undead to follow his master's directive through sheer force of will for 300 years.
Fate's female minions act like this toward him as well. He took them all in as children after their parents were killed in the war.
The Familiars and Wolkenritter of Lyrical Nanoha. If it's for the sake of their master, the rightness or wrongness of an act doesn't matter, and if it will benefit or save their master, they will gladly give up their lives, powers, and/or freedom.
In the Wolkenritter's case, this overlaps with My Master, Right or Wrong, as it was implied that some of the masters of the Book of Darkness were evil. This makes itself prominent in A's, where Signum stated they would gladly throw their honor away if it means saving their mistress as well as during StrikerS where Vita stated that she did not have any plans of outliving Hayate.
Fate Testarossa as well, initially toward Precia, then Nanoha.
Several of the Numbers have this towards each other, most of them going so far as to declare that where one goes, they'll follow. Case in point: Sette to Tre.
R.E.O Speedwagon from JoJo's Bizarre Adventure is extremely loyal to Jonathan Joestar via Defeat Means Friendship, combined with his selfless rescue of him from a burning building/Vampire attack. This loyalty would extend to the entire Joestar family, even more than half a century later.
On the villain side, we have Vanilla Ice (Don't ask). How loyal is he? He CUTS OFF HIS OWN HEAD WHEN DIO SAYS HE NEEDS BLOOD. Dio actually turns Ice into a Vampire in thanks for this. When he fights Iggy and Polneraff, he delivers a No-Holds-Barred Beatdown to Iggy just for making him destroy an effigy of Dio.
In One Piece, each of the Straw Hats are fiercely loyal to their captain Luffy, ready to risk their lives for him as soon as he gives the word. At one point, when Kuma wanted to kill Luffy, both Zoro and Sanji, without a moment of hesitation, offered their lives instead. And, of course, this loyalty goes both ways. Luffy is willing to die for his crew.
It seems Donquixote Doflamingo's crew have absolute loyalty and faith in Doflamingo, even to the point of death. Doflamingo himself seems to care for his crew, but that does not stop him from letting them kill themselves for him.
Deconstructed in the anime Gungrave. Brandon's personal code which is this trope puts him under much torment when he has to choose between the best friend Harry and the father figure Big Daddy. Brandon's inability to choose ends up being one of the main causes of Brandon's downfall, which in turn leads to suffering of the people closest to Brandon. In the finale, Brandon admits that even though he is supposed to enforce the iron law of the syndicate to never betray, he just cannot shoot his best friend Harry.
Loyalty is a big deal in the Sengoku Basara anime and games, given the subject matter, but Kojuuro and the rest of the Date clan really stand out in their loyalty to Date Masamune. In the anime's second season, Masamune's followers pile onto him bodily to protect him from Toyotomi Hideyoshi; a flashback in the following episode shows Kojuuro preparing to commit seppuku because he blamed himself for Masamune's arm being wounded in battle.
Yukimura's loyalty to his master Shingen is completely unfathomable. He can't even imagine a world where the latter doesn't exist for him to serve.
Hagi in Blood+ is characterized almost entirely by his unswerving loyalty to Saya. In something of a deconstruction, Hagi's devotion makes him reluctant to speak out when Saya makes decisions that might be bad for her; he even promises to kill her once she succeeds in killing Diva, and it takes being confronted and berated by Saya's brother Kai before Hagi will admit that he would much rather not go through with it.
Habaek in The Bride Of The Water God gave his first bride Nakbin the right to order his death, tried to follow her in death when she died, endured being separated from his current love Soah just to be with the resurrected Nakbin and when she died again, he honored her command not to look at someone with the same loving eyes he used to look at her even to Soah when he specifically told her that he will look at Soah only with his one eye (metaphorically though since his damaged eye is completely healed as a god.)
The Mustang unit to their commanding officer (and also to one another). Particularly true of Hawkeye, who at one point refuses Mustang's direct order to abandon him and save herself if his attempt to expose the Government Conspiracy fails. It cuts both ways: Mustang will do anything to protect his subordinates (again, particularly Hawkeye, to the point of jeopardising a secret mission to save her).
Fu and Lan Fan to Ling
And of course, the Elric brothers to one another.
The Briggs Brigade to Major-General Armstrong; Pride to Father.
A villain example but in Monster, Psycho for Hire Roberto is unfailingly loyal to his master Johan Liebert. Though given that this is Johan Liebert, a man often compared to Hitler and the Devil himself, it's unlikely that he feels the same.
Tsukishima has an ability to deliberately invoke this trope to anyone he cuts. His power allows him to manipulate existing bonds so that a false bond between himself and the victim can be inserted and supercede the bond it's designed to override.
When Byakuya is brainwashed, his loyalty to Ichigo is so extreme that it gives him the power to kill his enemy - not because the brainwashing failed, but because he would even kill someone he loved if they were an enemy of Ichigo's. Tsukishima learned the hard way that he had manipulated the wrong bond when he discovered that the emotional bond that most motivated Byakuya wasn't the bond between mentor and student, it was the bond between Byakuya and Ichigo.
Tsukishima has an Undying Loyalty of his own. Ginjou was everything to him, having found him and looked after him from the time Tsukishima had been a small child. Tsukishima admits that Ginjou had taught him everything... except how to live without him.
Komamura'sUndying Loyalty to Yamamoto stems from Yamamoto having once saved his life and always treating him well despite his appearance. When Yamamoto enters battle against the Stern Ritters, both he and the Seventh Division are on the verge of catastrophic defeat. His response to Yamamoto's resolve to fight is to rally both himself and the entire Seventh Division, much to the disbelief of Bambietta who had thought she'd won and all but killed the squad.
Katagiri was raised to be Ryuuken's personal servant and bodyguard. She will protect him no matter what the cost and her loyalty is to Ryuuken personally, over and above her loyalty to the Ishida family. So, when he believes he's failed his entire clan and tries to slink off forever into the Grey Rain Of Depression, Katagiri tells him that if he leaves, she'll abandon everything to go with him. Her speech brings him back to his senses.
Three of Shishio Makoto's Juppongatana in Rurouni Kenshin display undying loyalty to him. Yumi uses herself as a distraction so that Shishio can stab Kenshin through her. Kamatari had to be deceived so that he did not follow Shishio in death. These two were in love with Shishio. The last, Houji, thoroughly subverts Evil Chancellor. He is evil and he's Shishio's majordomo but he is utterly devoted to his leader. Enough to take the blame for an unpopular plan and risk the ire of the other Juppongatana. Enough to follow Shishio into hell. Even Shishio himself acknowledges Houji's loyalty.
Lupin III: Inspector Zenigata has the ability (Depending on the Writer) to inspire this in cops from all over the world. His subordinates in the Japanese police have ignored orders from the Interpol to follow Zenigata, and in the special Voyage To Danger the Italian police, after trapping Lupin in an unescapable trap (Lupin himself was desperate), packed and let him go when they learned that Zenigata had been pulled from the case because if they got him in that occasion it would have meant that Zenigata hadn't been the one who arrested him.
In Ronin Warriors, the true virtue the Ancient One imbued in Anubis' armor turns out to be Loyalty. After his Heel-Face Turn, Anubis shows why the armor chose him, remaining loyal to the Ronin Warriors and the Ancient One's memory to the point of sacrificing himself to save the Warriors and Lady Kyra, the last member of the Ancient One's clan.
In Beelzebub, the King's Crest is granted to those whose allegiance is sworn to a demon lord, which gives them a massive power boost. As of Chapter 217, it has been revealed that all four members of the Tohoshinki bear Beel's King's Crest, all but stating that in some way, all of them are loyal to Oga (even if they never admit it).
Despite the fact that their boss Dilandau treats them horrendously the Dragon Slayers in Vision of Escaflowne are this to him literally, since even after Van kills all of them their spirits intervene in order to protect Dilandau and allow him to escape.
Batman has had his ups and downs throughout the years, and had his scrapes with many a hero, but he will never be abandoned by Alfred.
Alfred: So that we can learn to pick ourselves up.
Bruce: You still haven't given up on me?
Well, usually. Sometimes Batman's jerkiness is too much for him and he'll leave for a time. "Venom" and "Officer Down" are two such stories where this happened.
I remember than Alfred quit when Bruce has decided to ruthlessly risk his own life only for his stubborness. Alfred said that he would not allow him to destroy himself and so, by abandoning Batman he could show his true loyalty to him.
Red Robin/Tim Drake is this. Batman notes that loyalty is his prime motivation, and his loyalty to his father caused his 10-Minute Retirement. So when Batman apparently dies, he goes Darker and Edgier, and tries to prove he is alive. Undying loyalty doesn't change regardless of who dies.
Wong, Doctor Strange's manservant and friend, is his one constant companion. He even sticks around after Strange relinquishes the title of Sorcerer Supreme and joins the New Avengers.
Wong's loyalty is most assuredly returned. In the Doctor Strange story, "The Oath", Strange goes through great lengths to save his manservant when he discovers Wong is suffering from an inoperable brain tumor.
Harley Quinn to her "puddin'". Of course given that this is the Joker we're talking about it is not returned. Death Of The Family subverts it. She ends up fighting back, and escapes him. She also declares that while she may love him, that does not mean that she belongs to him.
In Star WarsLegacy, this is expected of all of the One Sith towards their Dark Lord, Darth Krayt, and his cause. In practice, however, considering how ambition is a cardinal Sith trait, the main Sith characters tend to interpret this very differently:
Darth Talon is easily the most loyal to Krayt personally; she makes it plain she'd kill herself if she thought he needed her too and after he comes Back from the Dead, she's the first he contacts.
Darth Stryfe is totally loyal to the position of Dark Lord, which normally means Krayt, and he's not exactly shy about making sure everyone knows. However, when Krayt and Wyyrlok fight it out for the title, Stryfe stays out of it, assuming that whoever wins will be the superior leader. When that's Krayt, Stryfe reaffirms his loyalty.
Darth Maladi is more ambiguous; she's loyal to Krayt, but unlike the above two she's perfectly willing to question his judgment or operate independantly for a time if it suits her. At the end of the day, though, everything she does is ultimately put to the use of Krayt's cause, though Krayt himself thinks Maladi would do it all for its own sake anyway.
Darth Nihl defies this; he was an independant warlord before he was a Sith, and he's loyal to Krayt only for the power he grants his followers and fairly openly questions him and schemes against him. When Krayt dies his final death, Nihl immediately takes command, has Krayt's Elite Mooks killed when they object, and gets the heck out of dodge.
Darth Wyyrlok III is easily the most interesting. He is absolutely loyal- to the Sith cause, which Krayt and everyone else takes to mean loyalty to Krayt himself. Not quite. When Krayt goes into an extended Villainous Breakdown, Wyyrlok decides he's become a liability, promptly kills him off, and takes command himself, all in the name of the greater glory of the Sith. Pity for Wyyrlok that Krayt Came Back Strong...
It's rather disturbing to see how unflinchingly loyal most of the minions of the Red Skull are to their horrible monster of a boss. Of course, most of them are almost as evil as him.
A prime example of Anguirus's loyalty towards Godzilla can be seen in the 1974 film Godzilla vs. Mechagodzilla. In it, after losing to the Mechagodzilla (disguised as the real Godzilla) he goes to warn Godzilla about the impending danger even after Mechagodzilla had broken Anguirus's jaw and pretty much beat the living daylights out of him.
In Godzilla Final Wars, Anguirus is released by the Xilians alongside Rodan and King Caesar (Godzilla's other two allies in the Showa series) to stop Godzilla at Mount Fuji. Anguirus and Godzilla have a short conversation before Godzilla gives a sharp backward jerk of his head after Anguirus roars something and charges into battle, as if he's shocked that Anguirus would actually fight against him. Fortunately, Godzilla leaves his three former allies in a comical heap, sparing them from death.
Bob from the 1989 Batman film proves this trope isn't just for good characters. He always, always has The Joker's back covered and follows his boss' every order without question, even when Joker asks to borrow Bob's gun so he can shoot Bob dead just for the hell of it.
By the end of Star Trek Into Darkness, it's become obvious that the crew of the Enterprise have developed this with one another after they refused Spock's orders to abandon ship. Even early into the movie, both Scott and Spock continue to refer to Kirk as Captain despite him (temporarily) losing his rank.
Harada to Mariko in The Wolverine, despite his allegiance with Viper.
Hagrid is extremely loyal to Dumbledore in Harry Potter, probably moreso than any other person.
Sirius Black has put himself through a lot out of loyalty to Harry and his father.
Possibly the best example in the series of this trope is Severus Snape; we don't learn the circumstances until the end of the last book, though it has defined him the whole time.
Also, Ron's loyalty to Harry is repeatedly mentioned. They have a couple of instances where they're on the outs (they are teenage boys), but on the whole they're practically brothers. The "practically" is erased after Harry marries Ginny in the epilogue.
Harry's loyalty to Dumbledore is tested throughout books 5, 6, and 7. Even after learning about Dumbledore's Dark and Troubled Past and his Feet of Clay, Harry's loyalty to his mentor is unquestionable. "Dumbledore's man, through and through" indeed.
Villainous example: Bellatrix Lestrange is completely loyal to Voldemort, to the point of proudly going to Azkaban for him.
A prime example: Aragorn, Gimli and Legolas spend several days giving chase on foot to the orcs who captured Merry and Pippin. Aragorn outright states that they will continue looking for them even if in the end all they can do for them is starve to death together.
Also, Merry towards Éowyn and Pippin towards Faramir. For that matter, Éowyn towards Théoden.
Boxer, the horse in Animal Farm. "Napoleon is always right." Unfortunately, Napoleon didn't return the sentiments... Particularly tragic because the reason Boxer outlived his use was he was working extra hard to please Napoleon.
Mara Jade isn't the kind to give away her loyalty easily, but when she does, she'll defend whatever she chose with her life. She tends to be loyal to specific people rather than a large group; to Palpatine as an Emperor's Hand, to Talon Karrde as a smuggler, and to Luke and Ben as a Jedi, wife and mother.
The Dresden Files: Harry Dresden and Thomas Raith, the first because he never had any family aside from his father who died when he was small, and Thomas because his family was so messed up that he always protected his siblings, and that was the attitude Lord Raith instilled in his family (as a method of control), especially, his younger siblings, i.e. Harry and Inari. Family is important.
Harry: *in Proven Guilty when they are about to attack Arctis Tor, and having given a you don't have to come with me speech, his companions all step forward* I don't care whose DNA recombined with whose. When everything goes to hell, the people who stand by you without flinching - they are your family.
In the later books, he develops this with Murphy too.
Karrin:"Don't you start taking the highway to Hell. Because I'm going to be right there with you. All the way."
Molly to Harry. Harry's not too happy about this, given all of the questionable deeds she's done for his sake. Mab goes so far as to compare him to his old Evil Mentor Justin.
Andrew LaFollet in Honor Harrington is the titular character's personal armsman, sworn to die for her service if necessary. Despite Honor's trying to save him as the last surviving original armsman by having him guard her son, he dies saving his half sister and Honor's son and mother
Not just Andrew, but ALL of her armsmen display this. It's a 100% volunteer service and they all joined as they feel they owe a personal debt to her.
Then there's Horace Harkness's loyalty to Manticore. Caught, given a chance to surrender and or die, he switches sides. Then proceeds to manipulate his keepers until he can personally free his commander in a rather epic way.
Lord Byron wrote a poem dedicated to a beloved dog who died of rabies titled Epitaph to a Dog. The dog's unflinching love and loyalty are described in great detail:
But the poor Dog, in life the firmest friend The first to welcome, foremost to defend Whose honest heart is still his Masters own Who labours, fights, lives, breathes for him alone
In Dune the servitors of the Atreides except Yueh are loyal to their House. And even Yueh took steps to ensure that Paul and Jessica would survive his betrayal. Duncan Idaho sacrifices himself to buy time for Paul and Jessica's escape, Gurney Halleck quickly renews his service to Paul when he discovers he is alive, and Thufir Hawat kills himself rather than follow through on orders from the Emperor to kill Paul.
Thufir: You see, your Majesty? See your traitor's needle? Did you think that I who swore my life to the Atreides would give them less now?
The Atreides dukes are similarly loyal and protective toward their retainers. Paul Atreides is even willing to sacrifice his life to save the much, much older Hawat:
Paul: "For I say to you, Thufir, that in payment for your years of service to my family you may now ask anything you wish of me. Anything at all. Do you need my life now, Thufir? It is yours."
"Your friend Conseil," the fine lad replied serenely, "has nothing to say for himself. He's a completely disinterested party on this question... He's in Master's employ, he thinks like Master, he speaks like Master, and much to his regret, he can't be counted on to form a majority. Only two persons face each other here: Master on one side, Ned Land on the other. That said, your friend Conseil is listening, and he's ready to keep score."
I couldn't help smiling as Conseil wiped himself out of existence.
Catelyn orders Brienne to bring Sansa back to her from King's Landing. By the time she arrives, Sansa is no longer there, so she starts searching for her desperately, despite the dangers of the road and the fact that Catelyn is already dead by the time, and there is no safe place where she could bring Sansa anyway.
House Manderly is the only Andal noble house in the North. They were taken in long ago by the Starks and given the key port of White Harbor. They have repaid the debt with utter loyalty. The North Remembers
The entire North(except for the Boltons and possibly the Ryswells and Dustins) exhibit this trope towards the Starks. The Northmen,lord and commoner alike are prepared to march through blizzards,bone chilling cold in a state of near starvation or keep on fighting even when all hope is faded,for the sake of the Starks.
The Kingsguard are supposed to be this in regards to the King of Westeros. Jaime Lannister is reviled as The Oathbreaker for betraying his vows, even though everyone knows that Aerys II was a madman.
Luca Brasi from The Godfather has this towards VitoCorleone. In the backstory it is mentioned that during the Olive Oil War some mobsters tried to kill Vito and Luca proceeded to go on a Roaring Rampage of Revenge that only ended when Vito became well enough to call him off. However, this trait ultimatly backfires on him when Vito has him pretend to leave the Corleone family to inflitrate a rival mafia family and they see right through it.
Sancho Panza claims to be this for Don QuixoteEbut there are limits for the patience to the service to a Lord Error-Prone who always manages to get himself and Sancho in an Humiliation CongaOnce A Chapter. Sancho considers several times in the book to left Don Quixote service, but he is so fond of him he never does it.
...if I were wise I should have left my master long ago; but this was my fate, this was my bad luck; I can't help it, I must follow him; we're from the same village, I've eaten his bread, I'm fond of him, I'm grateful, he gave me his ass-colts, and above all I'm faithful; so it's quite impossible for anything to separate us, except the pickaxe and shovel.
The first book of The Sword of Truth series is dealing with a ritual the Big Bad uses to get into the world of the dead and back. It involves brainwashing a young boy into complete loyalty, killing him (by making him drink molten lead), and then using his spirit to travel to the underworld and back. As a case of taking the trope Up to Eleven, the boy must remain loyal until the traveler returns. In a later book, Richard uses this ritual as well, except he already had a spirit loyal enough to him since book one.
Song at Dawn: According to Raoulf, all soldiers should have this for their liege lord.
Raoulf: Shes just a woman. Hes your liege Lord, my boy and if it was you instead that he wanted, Viking fashion, why youd just have to bend over and take it.
The A-Team: So very much. Their loyalty to one another is so strong that in the beginning of Season 5, Hannibal, Face, and B.A. are willing to face the firing squad so Murdock won't have to. Don't worry. They all make it out just fine. And in the second season episode, Curtain Call, Face makes it quite clear that he is willing to risk capture/being sent to prison in order to get the proper medical supplies to save Murdock's life. And those are just two examples. The whole show is filled with moments like those.
Also Ranger Marcus Cole to Delenn, who once fought a Duel to the Death against a rival Warrior who wanted to assassinate her. The fact that she could inspire such loyalty, particularly in a human, convinced her rival that she deserved leadership of the Rangers.
Breaking Bad: This trope is lampshaded with near Once an Episode regularity regarding Walt and Jesse. It's a rather interesting case, as they're frequently at each other's throats, sometimes just because they're mad at one another, and sometimes much more seriously than that. Mike mentions it more than others as he is fond of Jesse's loyalty, but loathes who the loyalty is directed at. Towards the end of the half-fifth season, Jesse breaks it when he finally realizes how far Walt has gone and and he, himself, becomes The Atoner.
Chuck: Loyalty is a common theme, but perhaps most notable in Morgan. He repeatedly risks life and limb for the gang without a moment's hesitation. He's so loyal and daring that even Casey is impressed.
Doctor Who: Rory Williams. Rather than jumping forward in time with the Doctor, quick and easy, he chooses to stay behind and guard the Pandorica for 2,000 years (knowing that he will be conscious the whole time) to ensure that Amy is safe locked inside of it, despite the Doctor assuring him that Amy will be fine and warning him that the wait will drive him insane. Not even a little inconvenience like being erased from history is going to keep him away from Amy.
Dr. Simon Tam is devoted to being The Caretaker and when required the Papa Wolf to his disturbed little sister River. Naturally she responds in the Big Damn Movie. In his case he usually leads because he is of course the big brother. He is like Sam Gamgee very much of a Determinator.
Most of the team (actually, both teams) towards each other, but especially the core family of Peter, Walter, and Olivia.
In later seasons, Lincoln Lee in both universes comes to be one of the most loyal characters in the show.
Also, heartbreakingly, Nina towards the end of Season 5.
Game of Thrones: While House Tyrell joined the Lannisters out of a desire to gain more political power, Ser Loras Tyrell himself only wanted to avenge Lord Renly Baratheon's murder. Commanding a cavalry charge while wearing his deceased lover's armour is quite a grand romantic gesture, as it was Loras' way of honouring the vow he had made to Renly in Season 1.
Gossip Girl: Dorota is always loyal to Blair on , no matter what happens. Chuck Bass is also incredibly loyal...most of the time.
Inspector Lynley: DI Thomas Lynley and his partner DS Barbara Havers, to each other. Any attempt to turn them against each other will fail.
Law & Order: The partnered detectives on these shows frequently exhibit this toward each other, although Goren and Eames on Criminal Intent are perhaps the franchise's Trope Codifier. Eames even went so far as to resign from the force after Goren was fired in the season 9 opener.
Lexx: Kai is a dead assassin who has been reanimated. He has no emotions and no motives, but for some reason, he always sets out to save Stan and Xev.
Logan's Run: Rem: In the first episode of the TV series, Logan and Jessica meet Rem, an android. He helps them escape from other androids, then is completely loyal to them for the rest of the series, although he has no reason to do so, even putting himself at risk of being destroyed several times to save them, sometimes harming other humans in the process. He's not programmed to do this. He just does it.
Married... with Children: Al Bundy is this toward his wife Peggy, even if he hates the marriage with a passion and wish for it to be undone, as since anytime another woman offer herself to him, he'll (grudgingly) reject the offer in respect to his wife. Sure, he'll cry afterward but you've to give him credit for the loyalty he shows to something he always says he hates with every fiber in his body.
The Mentalist: Lisbon towards her entire team - but especially towards Jane. For him she's blackmailed one of her closest friends, blackmailed her boss's boss, punched a robber in order to get his case thrown out of court, gotten locked in a box, and repeatedly gotten suspended from the job that is basically her whole life. Not to mention six months of anger management classes.
Merlin to his loved ones, particularly Arthur, Guinevere, Morgana (before her Heel-Face Turn) and Gaius.
No matter what happens, he always stands by Arthur, and by extension albeit very reluctantly, Uther.
Lancelot to Gwen and the Knights to Arthur.
Against all legendary expectations, Guinevere to Arthur. Morgana had to resort to enchantments to force her into cheating on him with Lancelot. Even after Arthur banishes her from Camelot after believing her unfaithful, she continues to wear her engagement ring around her neck, and comes to his aid in his hour of need.
The Guardians, along with Roan, are completely loyal to Percy, and remain so even after Oversight locks him up at the beginning of Season 2, eventually helping him escape.
Michael, when he was The Dragon, also qualified, remaining loyal to Percy despite his misgivings about the latter's methods. That is, until he discovered that Percy was behind the murder of his family, which is what prompted his Heel-Face Turn.
Orphan Black: Foster siblings Sarah and Felix are very loyal to one another, mostly to Felix's detriment.
Revolution: A number of Monroe militia soldiers display this toward Sebastian Monroe. However, it seems to be mostly due to fear rather than an actual loyalty, considering how foolish and deranged Monroe is. Still, Jeremy Baker, one of his oldest friends stuck with him in "The Longest Day". When Monroe is about to have Baker executed out of paranoia, Baker gives him a speech about how Miles Matheson and Tom Neville betrayed Monroe because Monroe made them do so, Baker stuck with him through it all because he thought they were making a better world, Monroe will be all alone when he conquers the continent, and that Baker wouldn't wish that on his worst enemy, let alone his friend.
Rome: Vorenus. Once he swears fidelity to a cause or a person he will remain loyal to the end. Or as Octavian puts it, "The man turns loyalty into a vice."
The Sarah Connor Chronicles: Cameron is completely loyal to John Connor, and perfectly willing to be destroyed to protect him, to the point that she implants a bomb in her head and gives the detonator to John in case she "goes bad." This is juxtaposed with a termination protocol that Skynet hardwired into her to kill John Connor specifically, which activates when she takes severe damage at the start of the series' second season. She is eventually able to override this protocol, but her fears that the damage she took will make her hostile again form a major part of her internal conflict over the series.
Scrubs: JD towards Dr. Cox, one of the most prominent hallmarks of their relationship, especially whenever Cox is pitted against an outsider (or Kelso).
Sherlock: John Watson. He refused to believe that his best friend was a fraud, even when Sherlock himselfnote under duress from Moriarty, who'd threatened to kill John and everyone else Sherlock cared about was telling him so before jumping off a rooftop to his 'death'.
Chloe: I'd never tell anyone (about his secret). I'd die before I'd ever betray you.
Stargate SG-1: Samantha Carter would walk through fire for Jack O'Neill. Jack O'Neill "would rather die than lose Carter." And of course, SG-1 "is a team. No one else can begin to understand what that really means."
The Winchester boys take the "undying" part literally.
This is Meg's central defining character trait, and possibly the only reason she's been able to slide so far into heroic sociopath territory, despite committing numerous atrocities completely unapologetically and being Lucifer's staunchest supporter. At one point, she gives Dean a speech about why she didn't sell them out, ending with the line: "I'm talking cause, douchebag, as in reason to get up in the morning"
Since the show is basically about family relationships, this trait is fairly common. Other characters who exhibit strong tendencies towards loyalty include John, Bobby, Cas (before and after the civil war lead to the complete breakdown of his moral code), Balthazar (towards Cas), Gabriel (towards Lucifer and Michel), Rufus (towards his dead wife and Bobby), Ellen and Joe. The Monster of the Week episodes frequently feature humans and monsters who readily sacrifice their lives or hang around after death in order to protect their loved ones.
In The Thick of It, a series where every other professional alliance and relationship is completely destroyed at least once, Sam stays on as Malcolm's PA for the entirety of the show's eight year run.
Special note must be taken of Charlie Young and his utter devotion to the President. How strong is this man's loyalty to his boss? The Secret Service cannot keep him away from President Barlett during a White House lockdown. And in the episode "Two Cathedrals", Charlie forgoes wearing a raincoat out into a hurricane's bow, just because the president chooses not to wear one.
The X-Files: It doesn't seem to matter what you throw at them, nothing so far discovered can break Mulder and Scully apart for more than a few hours - and even then, they just rebound with a tighter bond than before.
Bianca Ryan 's song "I Will" is practically made of this:
I will come running to you
Nothing I wouldn't do.
I will never desert you, hurt you
I want you to know.
VOiCE is a pretty upbeat song about a robot and his undying loyalty to his master (Hatsune Miku) who was taken away from him because of a war. Even till his last breath, he still protects his master's house, hoping to see her one more time.
Legend of the Five Rings gives us the story of the Scorpion Clan Champion Bayushi Ujiro and his bodyguard Shunsen. Ujiro issued a challenge to the other Clan champions to determine which clan best understood the concept of loyalty. The challenge involved all the champions and their bodyguards performing an action to be set by Ujiro. If the bodyguards do not follow through with the command, that clan is disqualified. So, Ujiro gives Shunsen the command, "Kill me."He did, then commited suicide. The gathered Clan champions and bodyguards, shocked, conceded defeat. And then the Crane go and adapt the event for Winter, because that's just how the Crane are!
In Transformers, Megatron usually has at least one Decepticon like this. Soundwave gets a gold star for consistency; GLORIOUSLugnut for effort.
The Heroine to the Hero in Shin Megami Tensei I. She ditches her role as the Messiah to follow whatever he believes in. She's a bro.
Missile, from Ghost Trick, is literally the Most Triumphant Example. After he dies for the second time, this time with ghost tricks of his own, he opts to stay dead just to help save Lynne and Kamila. If that's not enough, the ending reveals that Ray is actually Missile from a previous Bad Future where he couldn't save anyone with his swap trick, so he goes back in time andwaits ten long years to make the black cat Sissel think he was the man in red, knowing that said main was tied to Lynne and Kamila's murders and Sissel is only concerned about discovering his identity. If that isn't the Crowning Moment of Undying Loyalty, what is?
In Professor Layton And The Miracle Mask, it's revealed at the end of the game that everything that Henry had done for the last 18 years was part of his effort to find Randall and prepare for his possible return. He even entered into a false marriage with Randall's girlfriend, Angela, just to save her from being essentially married-off to another man.
T3-M4 in Knights of the Old Republic: The Sith Lords (Contrast the first game, where his only sense of personality is as a foil to HK-47) is noted by other characters as being loyal to The Exile and becomes quite the sociopath (but played for laughs as his victims are droids) when she is captured by Goto and it needs to help rescue her.
Also from the second KotORevery single member of your party except Kreia due to the Jedi Exile's unique force bonds with them, and even Kreia likes the exile for being The Force's Übermensch.
HK-47 is himself an example, as he is loyal to Revan almost to the degree of hero-worship.
The two returning squadmates from ME1, Tali and Garrus, are already devoted to Shepard even before their loyalty missions in the second game. In particular, if you bring Garrus to the entrance of a quarantine zone for an epidemic that kills his species but not humans, he'll offer to follow you in even though you have human teammates available: "It's your call, Shepard. If you need me, I'm not going to let a damn cough keep me back."
Tali makes her hatred for Cerberus, the terrorist organization that Shepard is forced to work with in Mass Effect 2, clear from the very beginning and tells Shepard that she's only joining the mission for his/her sake.
Although she only joins the squad in DLC, you can learn that Liara's devotion to you drove her to absurd lengths between games. First, she went out of her way to find Shepard's body and prevent it from falling into the wrong hands. Then, she handed the body over to Cerberus despite her fears and mistrust of them because they were the only ones offering a small chance of Shepard coming back. Then, she embarked on a Roaring Rampage of Revenge against said "wrong hands", namely the Shadow Broker, the mightiest crime lord in the galaxy for daring to try to harm Shepard. And the reason she was so cold to you in the second game? She was scared senseless that Shepard Came Back Wrong due to Cerberus' manipulation. But even with that fear, her loyalty to Shepard's cause never wavered, maybe even being the most loyal to Shepard's cause, which is saying a lot.
In Grunt's case, even before his loyalty's solidified he pretty much already has nothing but total respect for Shepard and is quick to defend him/her to those who dare spit on his/her name. All thanks to their very first exchange, when Shepard stood up to him (when Grunt had him/her pinned against a wall) and had a gun on him without him noticing it. Being a total Badass will have that effect on krogan.
Then there's Joker and Dr. Chakwas who are willing to follow Shepard into hell and back and even join Cerberus partly because they were bringing Shepard back.
This loyalty also applies to Javik, the last of the Protheans. This is probably because Shepard helps Javiks personal mission to defeat the Reapers.
Shepard can even inspire this in people (s)he's only worked with once or twice: in Mass Effect 3, speaking to Kirrahe on the salarian homeworld will result in him promising to support you in retaking Earth, regardless of the salarian government's decision on the matter. If the salarian government does decide not to support you, most likely because you cured the krogan genophage against their wishes, Kirrahe goes AWOL in order to join you... and takes the entire salarian Special Tasks Group with him!
Both subverted and played straight with Miranda Lawson. Subverted with the Illusive Man, as while she consistently proclaimed her undying loyalty to him and Cerberus, she eventually lost her idealistic vision of the organization and made a Heel-Face Turn. Despite some initial tension, it is eventually played straight towards Shepard.
In Mass Effect 3, if the genophage is cured (and Wrex is still alive), then the entire krogan species get this towards humanity and Shepard in particular, with Wrex even promising that the krogan people would gladly lend areas of Tuchanka for displaced human refugees from Earth.
This point is finally rather unsubtly driven home in the "Citadel" DLC for ME3, where it is demonstrated that the main difference between Shepard and his/her secret Shadow Archetype clone is that the former has friends who'd walk into a fire for him/her, while the latter only has minions.
In Dragon Age: Origins, every party member's opinion of you will fluctuate depending on your actions. Be too evil and some will hate you, too noble, others likewise. It is possible to get them all to 100% approval, but their approval can drop without warning if you do the wrong thing in their eyes. The sole exception is your Mabari war hound, whose approval of you is eternally maxed out. Additionally, if the player character is of Human Nobleorigin, the Dog will have Undying Loyalty from even before the game starts. Little Daddy's Boy/Girl got a purebred Mabari pup sometime in the past and by the time of the game, that pup has become Dog.
Also, Alistair. All of the other humanoid party members can be asked/directed to leave the party, but that's not an option with him, and even if his opinion of you drops down to nothing he will stay with you. For Alistair, the Grey Warden order was the only family he ever truly had, and you are the only other surviving member of the group in Ferelden. He will only leave after the Landsmeet, if you decide to spare Loghain. It's actually a gameplay mechanic to ensure that there is at least one male Grey Warden at all times.
Dragon Age II promotes it to a gameplay mechanic: once you've maxed out a companion's Friendship or Rivalry, it will remain permanently locked there, signifying his or her unyielding loyalty to Hawke. In the endgame, this means that with a single exception (Sebastian, whose loyalty to the Chantry is greater than to Hawke), party members will stick with Hawke no matter what agenda s/he pursues.
Varric, in particular, never abandons Hawke and is even willing to kill old friends of his to protect him/her. At the end of the Legacy DLC, if done late in Act II or Act III, he tells of a conversation that Hawke has with his/her dead mother and admits that it didn't actually happen. He took the liberty because he wanted his friend to get the closure he felt s/he deserved but never got.
Generally, the noble antagonists in Fire Emblem have like this as a key character trait which leads to their death. Also Undying Loyalty to the main character is a common trait of most Jeigan characters including Jagen/Jeigan himself
Fire Emblem has a musical theme in several of the games called "A Knight's Oath." It plays when a character with a backstory in military service to the Hero's nation joins.
In Path of Radiance and Radiant Dawn there is also Soren, the very blunt cynical tactician who is distant and distrusts everyone... except his commander and best friend, Ike. His loyalty is so undying, that if he actually dies in the final chapter of the second game (he is ordinarily spared for plot reasons) his final words tell Ike that he must outlive armageddon, he tells multiple people including Ike himself that he will never leave Ike's side, and if Ike chooses to leave him behind? He still thinks about Ike for the rest of his life. Well, it's hard not to be loyal to the guy who was the first to treat you with any dignity at all and saved your life.
Ditto in Awakening between the Avatar and Chrom. Notably, Chrom returns the favor in a late-game confrontation, telling another hero who is threatening the Avatar that even if the latter is an unwilling Manchurian Agent for the Big Bad, he trusts him/her with his life.
Youmu from Touhou is intensely loyal to her mistress, Yuyuko. In the fighting game, Immaterial and Missing Power, Youmu briefly questions Yuyuko's actions but just as promptly castigates herself harshly for it.
Possibly the Trope Codifier for Video Game examples would have to be The Boss from Metal Gear Solid 3: Snake Eater. "Loyalty To The End." is her Badass Creed and her primary motivation to the exclusion of all else. The sheer scale of the sacrifices she makes in the name of that creed border on ridiculousness. In short (no easy task), she killed her own lover and father of her child under orders, was irradiated during nuclear testing, shot in the head, horrifically injured while being a top secret participant in the Mercury Project, betrayed all of her friends to their deaths and ultimately murdered by her most beloved pupil after a lifetime of painful sacrifices without solace or reward, and condemned to be remembered as a traitorous war criminal. All in the name of the United States government, which she had known since childhood to be corrupt from within by a dying conspiracy, and purely so that conspiracy could steal a huge amount of money from Russia. And yet, "Loyalty To The End." The revelation in Metal Gear Solid: Peace Walker that she was suffering from brain damage may undermine all this an iota however.
Gray Fox is another great example in this series. Raised as a child soldier in Africa during the Mozambique Civil War during the 1960s where he was nicknamed Frank Jaegar by his enemies for his "frank" appearance as a boy which he tricked them with until he killed them as a fierce "hunter" (Jaegar is German for hunter). Big Boss defeated the young Frank when he attacked him on patrol one day and rescued him from the war and brought him back to a U.S friendly safe zone but unfortunately the Philosophers experiment on him and turn him into a mind-controlled super soldier and years later Big Boss rescues him from this fate as well. Frank joins Big Boss's FOXHOUND Unit and from the 1970s until the 1990s serves under Big Boss's command in conflicts all around the world and earns their highest title of Fox, but despite his prowess as a warrior Fox tells Snake of how once again Big Boss came to his rescue when he had been captured by the enemy and they tortured him. In Gray Fox's eyes Big Boss is a father figure and the man to whom he owes his life; this undying loyalty to the man is so extreme that he betrays America and joins Big Boss's Outer Heaven cause even going so far as to fight his friend Solid Snake in a battle to the death. Fox's loyalty wasn't to a country or an ideal but to a man, Big Boss.
Kratos's feelings of loyalty toward Mithos have him lingering on the wrong side of morality for thousands of years, including nearly all of the game.
Botta's loyalty to his leader is his primary character trait, and even leads to his Heroic Sacrifice in order to save the party and thus make sure someone gets a message back to said leader.
Guy to Luke in Tales of the Abyss. Sure, he has a brief moment of weakness after Luke destroys Akzeriuth, but he's the only one who returns to Luke's side voluntarily. After that, nothing will keep Guy from backing Luke up. When Jade - in-universe, easily the most terrifying party member - suggests that Luke pull a Heroic Sacrifice, Guy lifts Jade the Necromancer off the ground by his collar. It gets to the point where he'll willingly hold Tear back, despite his pathological fear of touching women, at Luke's request, so Luke can perform said Heroic Sacrifice uninterrupted. Of course, as it happens, he's on the verge of tears.
Deekin in Neverwinter Nights is able to resist the Big Bad, one of the rulers of the Nine Hells, and who is simultaneously offering him great power to crush the Dragons he served under and is using his True Name to force him into helping. Merely telling Deekin you will miss him grants him will enough to fight off the most powerful magic in the planes.
''M: "Come, join me. What has done but hold you back from your potential? I could make you a force that all dragons would bow down to in fear! All the world would know your name, Deekin, and fear it!"
D: "No! You may be bigger than the boss, but... but... DEEKIN NOT LIKES YOU!!"
M: "You dare defy me, reptile?!"
D: "That's right! Deekin defies you! Deekin stands by the boss... to the end!" ''
In Final Fantasy IX, Steiner is portrayed as loyal to the royal family of Alexandria, there in which lies his personal conflict when he's forced to choose between loyalty to Queen Brahne and his sworn duty to protect Princess Garnet.
In God of War 3, the spirits of the fallen Spartans will come to Kratos' aid when he invokes the "Army of Sparta" magic. Even in death his soldiers remain loyal to him.
Sergei Vladimir to the Umbrella Corporation as a whole and Ozwell E. Spencer in particular in Resident Evil: The Umbrella Chronicles, for a stark contrast with his rival, AlbertWesker. Unlike most of his coworkers, he is absolutely determined to go down with the ship that is Umbrella; this largely stems from Umbrella having given him a home and a purpose following the collapse of the USSR. By the end of the game he's the only person still trying to hold Umbrella together, and he goes so far as to deliberately transform into a monster to try and stop Wesker from taking over the remnants of the company. When he dies, the company falls apart, as Sergei was the only one who was really keeping it intact.
Alfred Ashford displays similar tendencies with regards to his sister Alexia, to whom he is obsessively loyal, even going so far as to create a split personality version of her during her absence.
Fenrich to Valvatorez in Disgaea 4. Hell, Fenrich's Catch Phrase is "All is for my Lord". Doubles as a subversion to Fur Against Fang, with Fenrich and Valvatorez, respectively.
This is showcased rather tragically in The Legend of Zelda: Majora's Mask. The Ikana warriors encountered in the game guard the long abandoned and ruined Ikana Kingdom even in death, their ghoulish spirits still roam the area out of a devotion to their commander. Link encounters the Captain of the Guards in this area and helps him find peace so he can pass onto the afterlife at long last, his last order as the Captain he issues to Link to be the messenger, he tells Link to let his soldiers know that the war is over. When told this the soldiers in question finally let go of their obligation to the Kingdom and move on. The King of Ikana also still haunts his Kingdom and even in death he protects his throne when he sees Link thinking him to be an enemy. When Link defeats the King in battle he laments to Link his sadness over the fall of his Kingdom and how foolish he was to let it happen but he acknowledges that it is finally time to let go and rest in peace and as a parting gift he gives Link the tools he needs to defeat the final dungeon of the game.
Kid Icarus: Palutena, goddess of wisdom, gets this from her angel (who is pretty much her entire army), Pit. He is very quick to get into a shouting match with all sorts of divinities that insult her, and even when she was possessed and sent his lifeless body to slaughter untold amounts of innocent people, he gave everything to bring her back to herself again.
Captured Pokémon will follow a trainer's every command, provided they like the Trainer enough.
In Pokémon Black 2 and White 2 there is the Shadow Triad, three mysterious, shadowy figures who are utterly loyal to Ghestis for some unknown reason. Even when Ghestis is defeated and is driven mad, making him no longer a threat, they will show up at a spot every month, challenging you out of desire for revenge. (They won't force you, however.)
Before them, in HeartGold and SoulSilver, Archer, top Team Rocket executive, displayed this to Giovanni. Despite being the current boss of a powerful crime syndicate, his entire plan revolved around getting Giovanni to come out of hiding and reclaim his place as leader of the organization.
You have the option of releasing a Pokemon into the wild from the PC. If you try to do this to your very first Pokemon, it will comes back and the game tells you "It was worried about you." Even if you've kept it in the PC ever since that was allowed.
With the introduction of Pokemon Amie in Pokemon Xand Y, you can form close bonds with your Pokemon that can result in them overcoming status afflictions, dodging hits, hitting critically more often, and even REFUSING to faint all out of loyalty and love for their trainer.
Gardevoir, in particular, deserves special mention. Throughout the games, one fact continually gets mentioned in the Pokedex: It will protect its trainer, even at the cost of its own life. Damn...
A defining trait of the character Voldo is his great devotion to his long deceased master, Vercci.
IronTager is a field officer and research assistant working under Professor Kokonoe, and would follow any order she gives him with minimal hesitation - he may question it at first, but that doesn't stop him from obeying. He was an Ikarugan officer who was horribly injured during an operation to recover Deus Machina: Nirvana from the NOL, and Kokonoe literally had to reconstruct him into a demonesque cyborg. She wiped some of his memories of a particularly traumatic incident soon therafter, and had programmed him into total loyalty, but that is not to say programming and personality cannot overlap - even when he finds out about that incident, he is still loyal to her.
ValkenhaynR. Hellsing is one of the Six Heroes who fought off the BlackBeast over ninety years ago and is a massively hardened badass, but well before it erupted from the cauldron in Japan he was a mere vigilante. One of his missions set him upon Claudius Alucard, who while trouncing him offered him a position as a butler to his house - Valkenhayn accepted and has been loyal to Claudius ever since. When Claudius set out to help Jubei and Hakumen banish Terumi to the Boundary, Valkenhayn swore to look after his daughter Rachel - ninety years in multiple timelines has passed and not once has he swayed from that vow, and he is one of the very few people Rachel genuinely respects.
MakotoNanaya had faced some of the worst Fantastic Racism in the world and had grown a Jerkass Façade just to get away from it all, but found herself opening up to Noel and Tsubaki when they stood up to the "noble" twats that took it upon themselves to bully her. The three became very close friends over the Academy years, and she came to accept Jin and Carl as well. To say that her friends are the framework of her new identity is not hyperbole - her "unyielding will" is all her own, but for their sake she is not afraid to make the rest of the world her enemy, going so far as to defect from the NOL and send a thinly-veiled threat to Sector Seven through Tager just to protect Noel, and these bonds are literally half the reason (said "unyielding will" is the other half) she manages to survive a round trip between timelines through the friggin' Boundary.
Billy Kane of Fatal Fury and The King of Fighters is the right-hand man of Geese Howard. Before everything else, he is the right-hand man of Geese Howard. In the Maximum Impact sideseries, he abandons Southtown for England when Geese dies... but as soon as a new gang moves into Southtown, Billy goes back, because only Geese can rule Southtown. When fighting Rock Howard, Geese's son, Billy's prefight dialogue is anger that Rock isn't taking up Geese's legacy.
In Dishonored, there's a villainous example in the form of the Whalers to their leader, Daud. They are willing to risk their lives against a man more powerful and skilled than they are to defend Daud, and will only let Daud fight alone if he commands it; after being badly wounded so that he can no longer fight, Daud has to tell them to leave a second time to get them to back off. A heroic example is Corvo, who has Undying Loyalty to the Empress and her daughter, Emily.
In Assassin's Creed you gain people who will serve your cause with complete loyalty by saving them.
Several of the Servants in Fate/stay night would qualify. Saber, Berserker and Rider are probably the best examples, though the latter two are not immediately obvious. Archer has signs of this towards his master Rin from time to time despite flat out betraying her in the route centered around him.
Especially notable in Saber's case, as she was betrayed by Kiritsugu in Fate/Zero along with Irisviel, who she had true loyalty to. But even in arcs where Saber is bound and/or corrupted by magic, she still has an overriding protectiveness of Shirou.
None in the franchise embodies it more than the Fourth Grail War's Rider, Iskander, King of Conquerors, whose men are so loyal to him that he can create a Reality Marble from which to summon them to fight by his side once more. And later on, when Waver loses his Command Spells, Rider still sticks with him because, in his words, "Whether or not [you] are a Master, you are my friend, and that will never change."
In Skins Jordan has stood by her werewolf lover despite the terrible thing he did during the Kettletown mission. She even risks her own career to use an upcoming mission to give him a chance to redeem himself.
In Girl Genius All of the Jägers and the people of Mechanicsburg are loyal to the Heterodynes, to the point of twenty years later they are still waiting for them to come back.
General Goomblast explicitly states that the Jägers are voluntarily loyal to the Heterodynes, having made a solemn decision to serve the house for the rest of their unending lives before drinking the Super Serum that transformed them. The sole exception to this is Vole, who abandoned his oath, and is no longer considered a Jäger by the rest.
It seems as though this, more than anything, is what gave the Heterodyne's their power. Most Sparks use various flavors of mind control on their creations, who eventually turn on them. Most—if not all—Heterodyne creations serve their masters voluntarily, even after centuries of service.
Heterodynes, apparently, gain the loyalty of both their own creations and those of others by NOT demanding it.
Natural minions will remain loyal to their Sparks, even against their better judgment. Mechanicsburg, ancestral home of Heterodynes, happens to be completely populated with natural minions loyal to House Heterodyne.
Something Positive: The entire oddball band of True Companions has this as their primary virtue. Whatever else you can say about them, they're devoted to each other.
In The Challenges of Zona, Main Charecter Mentl uses this trope to describe his feelings for Zona, swearing that he would die beside her, and ordering her never to tell her to save himself after wiping out an army of monsters in a fireball that was hot enough to MELT the cave they were in to slag.
Durkon from The Order of the Stick is so loyal to his True Companions that he remains faithful to and helpful to them even after being killed, turned into a vampire, and his alignment shifted from Good to Evil.
Adventure Time: Marceline is shown to be incredibly loyal to Simon (AKA The Ice King) in the 5th season premier, where she, in an alternate reality where the Lich never existed, defended his body for 1000 years, making sure that nobody stole his crown.
Duck Dodgers used a variant which featured a robot (a rare Warner Bros. acknowledgment of The Iron Giant) serving as this to Dodgers, to the point of taking a meteor for Dodgers. In two different episodes.
The Cadet is also no slouch in this department. He keeps Dodgers out of trouble in spite of virtually never getting rewarded for it.
In the Shattered Glass continuity, where the Autobots are the villains and the Decepticons the heroes, Starscream is this to Megatron.
Soundwave in Transformers Prime is undyingly loyal to Megatron, to the point where his presence is probably the only thing that stops Starscream from pulling the plug on the Big Bad. This is pretty typical for Soundwave across multiple continuities, actually. Villain of the Week Skyquake displayed similar loyalty (and in fact took it to Lawful Stupid levels), refusing to work for Starscream because only Megatron could give him orders, and following the last set of orders Megatron gave him to the letter.
Skyquake's twin Dreadwing is also loyal to Megatron but he reaches his breaking point after his sense of honor clashes with Megatron's ruthless pragmatism.
Predaking pledges undying loyalty to Megatron after revealing his sentience, but Megatron remains suspicious. He tries to reduce the potential threat Predaking poses by wiping out the other Predacons, which backfires once Predaking finds out.
Ravage in Beast Wars. A former Decepticon rebuilt as a Predacon, he still remains loyal to the original Megatron long after the Great War. He is unimpressed by the current Megatron. Seeing the message the original Megatron inscribed on the Golden Disk convinces Ravage to help the current Megatron. When Rattrap manages to blow up Ravage's ship, Ravage's last words are "Decepticons, forever!"
Fry's dog Seymour in the Futurama episode "Jurassic Bark." The night before Fry was frozen, he told Seymour to wait for him, and he does just that. The dog spent the rest of it's life laying outside the pizza joint, year after year, waiting for his master to return until he ultimately dies of old age, and you have to watch it during the end credits. This was so heartbreaking that the creators ultimately retconned the entire thing with a complicated plot about time travel which involved a second Fry back in the past who stayed with the dog his entire life.
Rainbow Dash represents this as her Element of Harmony.
This is best demonstrated by the trial Nightmare Moon put her through in the second episode.
It is deconstructed by Discord in the second season premiere through a Sadistic Choice and Conflicting Loyaltywhat's more important — your friends, or your hometown?, with brainwashing thrown in for good measure.
In the season 3 episode where Rainbow Dash goes to the Wonderbolts Academy, after another recruit nearly KILLS her friends with a tornado, and shows NO remorse, she goes to Spitfire, the Wonderbolts' leader and says that if they're going to promote recklessness in the pursuit of improvement, then she QUITS! That's right, RAINBOW DASH, Ponyville's resident daredevil and speedster, who's been wanting to join the Wonderbolts since the PILOT, is willing to give up her greatest and dearest wish if it promotes the behavior that put her friends in mortal peril! Now THAT, THAT is loyalty.
Spike feels this way towards Twilight, as the 2nd episode of season 3 shows that his greatest fear is her not needing him anymore. Twilight's greatest fear, as shown in the same episode, is the same but with Celestia.
Naga is this for team Avatar, especially to Korra in The Legend of Korra. She even goes outside of Republic City to find Korra when Tarrlok captures her.
Kenny in South Park appears to be capable of this. In the movie he goes to hell so his friends can go back to the world as it was before the war. Also in a later episode he acted as a guardian angel for his sister Karen and protected her from bullies at school and their abusive agnostic foster parents.
While Pinky is usually a regular oblivious Bumbling Sidekick in Pinky and the Brain, his devotion to Brain is displayed in rather poignant levels at times. Despite the constant abuse and contempt Brain conveys over his stupidity, Pinky considers him his best friend and cheerfully goes through with every one of his orders. This is the guy who outright sold his soul to the devil in hope it could give Brain what he desired.
Darkseid is as villainous as you can get. Yet, when Superman defeats him with his own Omega Beams and throws him down to the slaves, what do they do? Carefully carry him away, genuinely worried about his safety. When Superman seems confused as to why people he believe he had freed would help him, Darkseid himself musters enough strength to answer:
Darkseid: I am many things, Kal-El. But here, I am God.
A lighter DCAU example is Jimmy Olsen. His loyalty to Superman never wavers, not even after Darkseid's brainwashing him has made him a pariah to most of the planet. When asked for his opinion by a news crew, he vehemently retorts, "Superman's saved the world a million times. We owe him another chance!"
Joseph Goebbels. He remained at Hitler's side until the last minutes of the battle of Berlin and committed suicide two days after Hitler did.
One German officer told a story from World War II when he was attached to a unit of Finns. The Russians abducted a wounded Finn and subjected him to Cold-Blooded Torture to lure his comrades to come to his aid and walk into an ambush. The Finns instinctively grabbed their weapons and walked into the forest knowing perfectly well what the Russians were up to.
At the beginning of the Winter War a party of Finnish soldiers went to the house of an old peasant woman and told her that the Russians were coming and they had to be deprived of shelter. She went into her hut, solemnly cleaned and swept it and then lit the fire herself. She said, "This is my gift to Finland."
During Stalingrad, a squad of Soviet troops were pinned down by German fire and tanks, with only one belt of ammo for their turret left. One of them gets captured by the Germans. The captured Soviet then lies to the Germans and tells them his squad is completely out of ammo, and leads them to the one place where he knows his squad will be able to mow down the Germans with what little firepower they have. The captured Soviet soldier was later executed in front of his still-pinned down comrades, who were eventually killed when the Germans called in tanks to run them out.
Marriage vows are often some form of a declaration of the trope:
Name, will you have this wo/man to be your husband/wife; to live together in the covenant of marriage? Will you love him, comfort him, honor and keep him, in sickness and in health; and, forsaking all others, be faithful to him as long as you both shall live?
Dogs to mankind. This dog, for example, refused to leave the casket of his Navy Seal master.
During the filming of Suburban Knights, things looked so hopeless during filming do to inclement weather and other issues that Doug, Rob, and Mike Michaud were all fully prepared to scrap the whole thing and simply film everyone hanging out in Chicago as the special. Holly told them everyone wanted to get the film done, so they tried to have a vote. Linkara stood up to say the voting was pointless, because they already knew everyone would say yes. He then went into a speech saying that Doug is the reason that every one of them has a job on the site, and they're going to finish this thing for him no matter what. Doug thanked them profusely and left, newly energized to figure out the best way to finish the film.
Some species of animal will remain faithful to their breeding partner for all its life. For example, the Shingleback has been known to even stay by the side of their partner if they die for days on end.