These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Acceptable Targets: Many Norsemen view Christians as this, and most Christians feel the same way about Pagans. There are a few exceptions on both sides, however.
Anti-Climax Boss: Lord Athelwulf, King Aelle's brother. He's called in by Aelle specifically to defend Northumbria from Ragnar, is praised as a battle commander, and does show some competence as a tactician when he reigns in a few leeroys on his team. The problem is that he completely fails to assign sentries at his camp, so his men are slaughtered in the night, and when he awakens, he spends a good two minutes praying before battle. By the time he's done, his men are soundly defeated, and he doesn't even make it out of his tent - Floki brings the thing down on him, capturing him without a fight.
Values Dissonance aside, some fans loathe Rollo for his background as an unrepentant rapist, and feel that his "redemption" character arc completely sweeps that issue under the rug. He's still a generally popular character.
Aslaug tends to provoke some mixed reactions from viewers, to put it lightly.
Specifically, in Boneless, Wardruna's Helvegen plays when the Vikings prepare to set off for Wessex again. May also be foreshadowing, as Helvegen is translated as "The Road To Hel."
If we thin about how that journey went, it certainly was forshadowing
Designated Hero: The Vikings as a whole, but Ragnar in particular. Though he's popular among most fans, there are those who will rightfully point out that he did betray his wife and family. Of course, Aslaug catches most the blame for that.
Earl Haraldson; in episodes 1-5, he displays extreme cruelty and pettiness. Among other things, he has a man unjustly executed and desecrates his body over a personal grudge, has one of his men killed for trying to sleep with his wife after he himself gives permission for it to happen, has his henchmen kill a thirteen year old boy, attempts to assassinate the protagonists (succeeding in killing at least one of them), launches a full on raid on Ragnar's village, slaughtering dozens just to get one man, and brutally tortures Rollo. However his death scene is so epic and so well acted that it managed to shift many people's opinion of him to Anti-Villain.
Erik is incredibly popular with the fandom. Primarily as a result of copious badassery, one-hit kills, and a stellar performance by Vladimir Kulich.
Tostig, the Old SoldierDeath Seeker, has become extremely popular as well, for similar reasons as Erik. Not the least of which for his epic speech - a tremendous reading by Angus MacInnes.
Floki has captured the hearts and minds of many in the fandom and has been called the the Viking version of the Joker.
King Ecbert has gained his fair share of admirers for his effective leadership, respect for pagan cultures, and for being the first non-Norse antagonist to give the Vikings a serious challenge.
Epileptic Trees: Ragnar Lodbrok was never a very important character in Norway, but after this show premiered he has gained a Periphery Demographic in said country who are sure that he is Norwegian because there are Fjords in Kattegatt! Nevermind that the show also depicts fjords in Uppsala and Hedeby. Ragnar Lodbrok is described in the Sagas as Swedish or Danish or a mixture of the two, but never Norwegian.
Finnish Strongman Jouko Ahola plays one of Ragnars men in season one, wich has lead some ambitious fans to enter him into That Other Wiki as A "Finnish Viking". Never mind the fact that we get to learn absolutely nothing about where this character hails from or even what he's called.
Ragnar and Athelstan. When Ragnar first finds Athelstan, he pushes him up against a wall and gets in real close. A few moments later Rollo walks in and dejectedly comments how there aren't any women in the monastery, and the group looks to Athelstan. Later, Ragnar invites Athelstan to have a threesome. And after the timeskip, his reactions to Athelstan's supposed death, Seer-prophesized survival, and arm ring are rather striking and emotional as well.
And let's not forget Athelstan volunteering to stay in Wessex to help Horik's men. Ragnar's entire disposition in that scene reads more like a jealous lover than a friend/commander.
And then there's the scene where Ragnar and Ecbert discuss a possible alliance while in the bathtub together, particularly the part when Ecbert stares at Ragnar as he undresses.
Growing the Beard: The first season showed that the network could do scripted drama and manage to look and feel like more than your typical hour long docu-type history lesson for which the channel is known. The second season upped the ante in terms of storytelling and production value turning a good series into an epic, while still maintaning realism.
Earl Haraldson kicks plenty of dogs, but he's also spent quite a lot of time mourning the horrific deaths of his sons and heirs. His death scene in particular makes it clear that while he is a petty tyrant who will kill innocents and torture men without regret, he's become so because he is a weary and deeply unhappy man who, in the end, welcomes death and smiles for the first and last time in the series as he dies.
To some, Jarl Borg can come off as either this or a Designated Villain. There's no question that he's an underhanded and ruthless warrior, but that really doesn't make him any worse than the protagonists. Horik dislikes him because of a long-standing dispute over land between them, but it's impossible to tell who was in the right on that one. Ragnar hates him because of his invasion and brief occupation of Kattegat. However, that assault was only in response to King Horik backing out of their alliance at the last possible moment, for petty reasons — which, given the relinquishment of his claim to Horik's land rested on Ragnar's promise of Western booty, was more or less an appropriate response by the laws of the time and the place. After Ragnar takes back his home and apparently forgives him, Borg swiftly admits that Ragnar is the better person, and genuinely seems open to making amends. However, this was all a cruel ploy on the part of Ragnar, who captures him and carves the Blood Eagle on him. These factors, combined with his tragic backstory and an absolutely epic Face Death With Dignity scene, can make it seem like all the hate he gets from the protagonists and portions of the fandom isn't completely merited.
Like You Would Really Do It: Trailers for Season 2 seemed to imply that Floki would be killed in battle by Rollo. Given the character's popularity, many fans suspected that this wouldn't be the case.
Magnificent Bastard: Ragnar for his balls and the savvy genius that lay behind the westward raids, befriending one of the greatest sources of information on the Christian world, and then manipulating and outwitting the Northumbrians afterwards. Basically, it doesn't matter if you're a jarl or a king, Ragnar will find a way to outmaneuver you and come out on top. It's taken Up to Eleven in the finale of Season 2.
Narm: Kwenthrith's obsession with sex and tendency to hit on anything with a penis can come off as unintentionally goofy and over the top.
Nightmare Fuel: The Blood Eagle, a horrific form of execution reserved for those who commit the most heinous crimes. When Ragnar is administering this punishment to Earl Borg, many of the battle-hardened viking warriors in attendance are clearly disturbed by it.
One-Scene Wonder: Tostig appears in several scenes in two episodes, but has little more than 5 minutes of screentime. Still many consider him one of the most memorable characters in the entire show.
OT 3: Athelstan/Ragnar/Lagertha. This is almost canon.
Tear Jerker: Ragnar's farewell to Gyda in Brother's War.
If comments from YouTube and various social media are any indication, Aslaug seems to be widely disliked by the fandom for helping to destroy the popular Ragnar/Lagertha relationship (though Ragnar bears an equal share of the blame on that one), and being, all in all, the grown up version of a spoiled, self-righteous brat who inherited none of her parents' heroic qualities. Doubly amusing when you realize Aslaug is the actual protagonist of the saga the show is based on. Less amusing when you realize that she is supposed to be a smart warrior princess in the saga while in the show, the "smart" part is reduced to having visions and the "warrior" part is non-existent.
While Horik, being Ragnar's rival, was never designed to be popular in the first place, he might currently be the most hated character on the show. He was already seen as the root of everything which went wrong in Season 2 for the protagonists, but when he called Athelstan a "worthless individual", believing him to be dead, fans started to declare that the blood eagle would be too good for him.
Ron the Death Eater: Aslaug. Many fans are willing to paint her as a home-wrecker or a spoiled brat when in fact she is far from either. Most of these fans are Lagertha fans obviously.
Too Cool to Live: Let's see, Erik... Badass warrior? Imposingly big and tall? Beard of a grizzly bear? Has one-hit kill as a default? Cool voice? Played by Vladimir Kulich? Got top-billing (in the guest starring part of the ending credits anyway)? Nope. Sorry. You're so awesome, you might overshadow the main character. So... off to Odin's Hall with you.
We Hardly Knew Ye: Erik (Vladimir Kulich) dies in the fourth episode. You may recognize him from previous badass Viking roles like Buliwyf and Ulfric Stormcloak, or just generally badass roles like the Swede from Smoking Aces.