As Game of Thrones deals with an evolving world where character motivations and situations drastically can turn in every season, Character Derailment was bound to occur with few characters.
- Doreah gets a very abrupt Face–Heel Turn. After a season of being a scrupulously loyal servant and supporter of Daenerys, she suddenly betrays her and gleefully murders one of her own friends. Because her character simply dies randomly in the original books, this was apparently seen as a more interesting end to her character.
- Shae takes a sudden veer into Clingy Jealous Girl on Tyrion without much preamble, feeling threatened for no real logical reason by Tyrion's marriage to Sansa. This was all ironically necessary because of her Adaptational Heroism: while in the books she is just a shallow opportunist who was playing Tyrion the whole time, in the show she honestly loves Tyrion, so the show has to make a sharp swerve to get her to betray him.
- Many complaints have been hurled at the show in Season 5 for how Sansa's been treated character wise since she's essentially taken over Jeyne Poole's role as Ramsay Bolton's wife/hostage/sex slave. Despite the previous season ending with Sansa helping Littlefinger cover up her aunt's murder and seemingly setting her up as becoming a Magnificent Bastard in her own right, this season she essentially becomes a Damsel in Distress who begs Reek to help her escape captivity after she was raped. The fact that Sansa is begging Reek for help is also considered out of character since she was shown to hate him for the supposed deaths of her little brothers and for betraying Robb and told him in no uncertain terms she didn't care what happened to him in the previous episode.
- Sansa's characterization in Season 8 takes away her cunning and political acumen to have her take foolish actions like being disrespectful in open court that realistically would get her censured, and make obvious moves like telling Jon's secret that the other characters should see coming a mile away but don't (except Daenerys, who is somehow punished for being right) because the script has dumbed them down, too. The only way she gets away with this behavior is because the plot says so. It's not even the fact that she's scheming so much as that it's not clever scheming. As a student of Littlefinger, if Sansa wanted to undermine Daenerys then realistically she would present herself as Dany's new best friend and confidant, not signal contempt from day one. This is particularly egregious because in the books, her personal mantra is "courtesy is a lady's armor". Of course, the show's version of Littlefinger, as even GRRM has complained about, is also subject to this by being Obviously Evil, whereas in the books he gets away with everything he does because no one suspects him.
- And there's the fact that this season Sansa is suddenly all about Northern independence when that's never been her cause before now, which comes off as either an eleventh-hour motive or just an insincere excuse to get herself a crown. She's so defined by her dislike of Dany this season, whom she barely bothers to get to know, that she's even reluctant to throw support behind her southern campaign against Cersei, whom she has genuine reason to hate. This seems quite out of character.
- And she talks about her previous innocence as if it was entirely a bad thing and the abuse she's suffered from her various tormentors has been good for her, while in fact losing some admirable qualities she displayed before - for example, while sheltering in the Red Keep during Stannis's attack on King's Landing in "Blackwater", Sansa in contrast to Cersei worked to keep the other ladies' spirits up. While sheltering in the Winterfell crypt in "The Long Night", she does nothing to comfort her people.
- Ellaria Sand in Season 4 tried to calm Oberyn down when he heard two Lannister soldiers singing "The Rains of Castamere". However in Season 5, she becomes very irrational and wanted to harm Myrcella, because she's a Lannister despite that she has nothing to do with her lover's death and regardless that Doran gave her a second chance with a warning, she still pursues her revenge by poisoning Myrcella while she's on her way back to King's Landing with Jaime and Bronn. In the season 6 premiere, she personally murders Doran and sends her daughters to kill Trystane because they don't support her revenge.
- Petyr Baelish, a.k.a. Littlefinger. It's made pretty clear in Season 4 that he's seeing Sansa as a replacement for her mother Catelyn Stark, the woman he was obsessed with. In Season 5 he doesn't hesitate for a second to send her up to the Boltons in the North to marry Ramsay. This may be justified as he says he doesn't know anything about Ramsay, but that still derails him as he's meant to be a great planner and information gatherer who wouldn't send Sansa to marry someone without knowing them well, especially as Ramsay has a reputation as The Dreaded throughout the North so Littlefinger should have known of his psychotic qualities, to the point Martin himself has also commented on this.G.R.R. Martin: My Littlefinger would never have turned Sansa over to Ramsay. Never. He's obsessed with her. Half the time he thinks she's the daughter he never had - that he wishes he'd had, if he'd married Catelyn. And half the time he thinks she is Catelyn, and he wants her for himself. He's not going to give her to someone who would do bad things to her. That's going to be very different in the books.
- Littlefinger's derailment reaches its peak in the Season 7 finale "The Dragon and the Wolf". Despite his reputation for out-thinking his enemies he is completely outsmarted and killed by Sansa and Arya because he doesn't think of any of the many options that could have saved him. He doesn't ask for a trial by combat, he doesn't ask to be sent to the Night's Watch, he doesn't try to poke any holes in Sansa and Bran's stories, and he doesn't even really try to deny any of the charges. And this is on top of him staying in Winterfell in the first place after he found out in a previous episode that Bran can see the past and thus knows about his many crimes.
- The Unsullied are initially introduced in Season 3 as invincible war-obsessed fighting machines. And at first, this seems to be true - they manage to capture Yunkai and Meereen with relative ease. In Season 5, however, they are somehow outmatched and easily defeated on several occasions by the Sons of the Harpy - shadowy Meereenese terrorists largely made up of former slaveowners with little to no combat training, and armed only with knives. In the books, the Sons largely attack civilians, only attacking Unsullied when they are alone and off-guard (such as in brothels), but their threatening nature seems to be increased for the adaptation.
- Jaime in the books realizes that a lot of his problems he's faced is because of being with Cersei in their secret affair, to the point of burning a letter she's written and sent to him ignoring her pleas to come and be her Champion in a Trial by Combat. In the series he looks to go through the same development as in the books but after Season 4 however, he becomes little more than her lapdog as he was before, going from the only person who ever loved his brother, to vowing to kill Tyrion after he had killed their father Tywin, and even tells Cersei "We're the only people who matter." Then in Season 7, he still remains on Cersei's side despite that she blew up the Sept of Baelor with wildfire, making her very similar to Aerys II the Mad King who he killed before. Fortunately, he undergoes some very satisfying Character Rerailment in the Season 7 finale. When Cersei reveals her plan to let the White Walkers destroy the North and thus risk the end of all Westeros just out of sheer spite and lust for power, Jaime promptly chews her out and leaves King's Landing, dumping her. Until his character arc derailed again for good in Season 8. Jaime fights on the side of the North and Dany to defeat the White Walkers, seemingly ready to settle down in the North with Brienne, when he suddenly decides to ride south to save Cersei from Dany's rampage on King's Landing, breaking Brienne's heart. The next episode includes lines from him that he doesn't really care about the common people (which he shows by not helping a single civilian escape the war), and tells Cersei that no one matters but them as he dies in her arms.
- Davos Seaworth has dedicated his entire life to King Stannis Baratheon after Stannis knighted him even though he punished Davos for his smuggling. He goes as far as declaring that "King Stannis is [his] God" in season 2. Other big parts of his character portrayal is his dislike for Lady Melisandre and his fondness of Stannis's daughter, Shireen, but apparently none of that is important once Stannis is killed in battle after sacrificing his daughter to the Red God, as aside from a heartbreaking but still very quick look of sadness when learning about Shireen's death, he seemingly immediately jumps into Team Jon Snow once Jon is also killed, betrayed by his own men. Davos takes several weeks to even question Melisandre about Stannis and Shireen's deaths, and puts aside his hatred for the woman, begging her for "any magic" in order to help Jon, whom he barely knew and had shared no scenes alone with so far.
- Euron Greyjoy during his introduction was genuinely terrifying (much like his book counterpart), where he killed his own brother Balon due to being a weak ruler who plunged the Ironborn into useless wars, while taking over the Ironborn rule by being a deviously charismatic man who openly admitted he murdered his brother despite kinslaying being a heinous crime (helped by Balon being unpopular), and proposing a plan to ally with Dany and her dragons, until Yara and Theon escaped and made his plan their own. Later appearances made Euron an Ax-Crazy lackey of Cersei whose goal is to impress Cersei, and delegated to counter Dany's advantages in the War for the Iron Throne. Despite cutting his losses and running from King's Landing to the Iron Islands is exactly what he would have done earlier in the face of a Zombie Apocalypse, he stays at Cersei's side and helps her kill Rhaegal and Missandei, despite him also being capable of inflicting greater damage even just for the kicks.
- Varys in the initial episodes used to be The Chessmaster, convincing Eddard to confess to treason despite Ned's infamous Honor Before Reason tendencies (it was reduced to null after Joffrey intervened, but Varys had no way to predict it given that Joffrey was slated to send him to Night's Watch), as well as meticulously planning King's Landing's defense in Season 2. It was also the reason Varys survived four volatile rulers (with Joffrey and Aerys having high-turnover rates, to put it mildly). Varys also was reputed to work behind the shadows, to the point Littlefinger, one of his intellectual equals barely kept up with him, due to Varys being enigmatic. He also supported Dany after hearing about how she freed the slaves in Slaver's Bay and suppressed the Masters, feeling she would be a just, fierce and kind ruler. All these went away in the final two seasons, where Varys is reduced to pleading Daenerys to allow him to work with her as Daenerys wanted to punish Varys for his supposed Chronic Backstabbing Disorder. But Varys's derailment hit its peak during the final episodes of Season 8, where after learning that Jon has the higher dynastic claim due to being the son of Rhaegar, Varys immediately abandons Daenerys due to his supposed Heir Club for Men attitude, even planning to poison Daenerys, despite her risking her life to save the realm from the White Walkers, and thus being one of the most ideal rulers by Varys's definition, who (while with all his faults) is truly loyal to the realm and the smallfolk. He then decides to talk to Jon in an attempt to turn him, thus advertising that he plans to commit treason against Dany, while knowing Jon is completely loyal to her. Even if Tyrion didn't blab about him, Jon would have, thus making it a very crucial mistake Varys would have never made earlier, which ultimately seals his fate. He never even tries to defend himself or flee her side after doing so.
- He also doesn't consider how Jon will keep control of Daenerys's armies, most of whom are loyal to her personally because they see her as a Messianic Archetype and not because of her Targaryen dynastic claim that Jon is supposedly ahead of her in line for. If she died at such a crucial juncture before Cersei was even defeated, the various factions like Dothraki, Northmen and Ironborn could easily turn on each other and destroy the war effort, to say nothing of her dragon (frankly, the fact that Drogon and Dany's most loyal followers don't raze the Seven Kingdoms after her actual onscreen death is unrealistic and only happens that way because the plot says so). And somehow Varys thinks that him sending the lords letters claiming that Jon is Lyanna and Rhaegar's son will be enough to convince them of such an extraordinary claim. In short, Varys of all people, whose schemes have been designed to take decades to come into effect, is suddenly acting with no plan.
- Jon Snow, most known for his leadership and his high moral standards, has both completely removed after he bends the knee to Daenerys. Afterward he becomes an Extreme Doormat with almost no agency of his own. This reaches its extreme in the penultimate episode "The Bells" where after Dany begins burning down all of King's Landing and Grey Worm and the Northerners begin murdering the surrendered Lannister soldiers and the innocent civilians, Jon just stands there for a moment drinking it in, then briefly tries to get his men to stop before getting attacked and then resuming to just stand around. While, to his credit, he does kill a Northerner when he to rape an innocent woman, Jon doesn't give the order to retreat until Daenerys starts burning close the men, well after Grey Worm and the others have killed most if not all the people. It somehow gets worse in series finale "The Iron Throne" when not only does Jon barely even try to stop Grey Worm from continuing to execute people, but he goes on to actually defend Daenerys burning all those people alive. It pretty much takes Tyrion pointing out that Arya and Sansa will never bend the knee to convince him to assassinate Daenerys.
- Arya also undergoes this in the final seasons. In Season 2, she proudly admitted to Tywin that she liked warrior women due to their will to defy gender roles, even namedropping Visenya Targaryen as one of her favorite rulers due to being battle-hardy with her dragon (which was an addition for the show, even, so the show writers ought to keep it in mind), and naming Nymeria after one of them. She also wanted to reunite with her family, only going to Braavos because she thought her family was dead or worse. In Season 8, despite Daenerys being a warrior queen in her own right and a powerful ally with two dragons, not to mention a descendant of the aforementioned Visenya and Nymeria, she rejects her due to not being from the North and is cold to her for no reason. She also leaves her family immediately after saying that they should stick together against future enemies, saying she will never return to her family again. And says they don't need allies from outside their family even though she herself hasn't followed this either before or after the odd scene where she said it.
- Although Daenerys has always been ruthless and there were hints of a darker side to her since the first season, her vengeful acts and "fire and blood" speeches were always balanced with acts of kindness or self-awareness, such as listening to her advisers to temper her worst impulses, and didn't want to harm those who didn't deserve it, or weren't part of an enemy army. While there's precedent for her being ruthless, there's none for her being irrational. When two of her dragons die, she loses half her forces, and Jon is revealed to have a better claim to the throne than she, her sanity deteriorates over the span of two episodes at the end of the last season to the point where she burns innocent civilians alive in King's Landing, after the city had surrendered and she'd already gotten what she wanted, so that she becomes the final boss of the series. Even with all she went through, there is no explanation as to where her compassion and self-awareness went or why she would suddenly attack a surrendered city and call it "necessary" after tacitly agreeing with Tyrion not to attack once the bells were rung. It has always been stressed that she does not have the hereditary Targaryen madness (and characters like Tywin and Tyrion Lannister, Robb, Sansa and Arya Stark, and Jon Snow, have undertaken similar actions without being deemed mad, simply evil, which Dany has no good reason to be). Furthermore, other characters in Season 8 like Varys and Sansa act as if she deserves to be seen this way very prematurely without her having done or said anything wrong yet, and after sacking the city she talks like a parody of herself, making it clear this derailment was a forced development in the narrative. Hell, four seasons earlier, she was left horrified to discover that her dragons had accidentally killed one three-year-old child, and so distraught she literally kept them chained underground.
- In the earlier seasons, Tyrion was mostly defined by his intelligence, his cleverness and his skill in strategy. However by the time Seasons 7 and 8 rolled around, he became incapable of making any smart or correct decisions, to the point where every plan of his in Seasons 7 and 8 backfires spectacularly. His plan to take Casterly Rock instead of the Red Keep effectively strands the Unsullied in a useless position and gets Obara, Nymeria and Tyene Sand and Olenna Tyrell all killed and Ellaria Sand imprisoned with no chance of rescue, somehow failing to notice the Lannister army crossing from one side of the continent to the other over what must have been many days to take Highgarden. Then his plan to capture a wight to prove their existence to Cersei gets Thoros of Myr, Benjen Stark and Daenerys's dragon Viserion all killed, and the Wall destroyed by Viserion and the Night King, while not resulting in any reinforcements from Cersei, whom he has known long enough (all his life) not to trust. Then, in Season 8, he has the civilians hide from the White Walkers that can bring the dead back to life in the crypt. Then he immediately and without prompting or permission tells Varys about Jon's true parentage after Sansa tells him, despite knowing that Varys marches to the beat of his own drum and the threat that information could pose to Jon and Daenerys both. Tyrion's newfound inability to think things through is mocked by Sansa, Dany, and even Peter Dinklage.Peter Dinklage: [The Night King]'s bringing all the dead people back to life, and they put the women and children in a crypt with all the dead people! So...rah. Tyrion is smart, but I guess not that smart.
