Vinland Saga takes place in the Viking Age, a bygone era where people did almost everything by hand, from household chores to chopping down trees and fighting their enemies on the field of battle. In this medieval world, it pays to be physically fit and strong, either to kill one's enemies or defend their loved ones from attack.
In Vinland Saga, not all the physically powerful characters are warriors, and not all the warriors rely entirely on brute strength to win. Even so, there's a strong correlation, and in Thorfinn's experience, strong and tough people tend to survive and are valuable to their communities. As a relatively fast but weak fighter, Thorfinn must respect how powerful these characters are and stay out of their way.
Update on June 21st, 2023: we have expanded this list once again to include Vinland Saga's strongest, most physically gifted characters who can swing a sword, row a ship, or just work all day in the fields without getting tired. In a pragmatic medival world like this one, it really is the strongest Vinland Saga characters who survive.
The following contains minor spoilers for the Vinland Saga manga.
20 Leif Ericson
Leif Ericson is the starry-eyed Viking explorer who found the New World in his youth, and he even befriended the Native Americans there and brought back a few gifts from them. This helped inspire Thorfinn Karlsefni to find the fabled Vinland for himself someday.
By this point in the manga and anime, poor Leif is a frail old man who can't go on adventures any longer. He ranks near the bottom of the strongest characters in Vinland Saga, but he doesn't mind. Leif had his fun, and now he's giving Thorfinn his blessing to carry on the spirit of exploration.
19 King Canute
Growing up, prince Canute was a total dandere who learned to be quiet and not upset anyone, or else he'd get himself killed by his family's violent politics. Canute still wanted to fight, though, and has been seen training with a sword to defend himself.
Now the king of Denmark and England, Canute projects confidence, wisdom, and strength as a well-balanced king. He's not the strongest swordsman, but hre has definitely gotten tougher and no longer relies so heavily on bodyguards to protect his person.
18 Bug-Eyes Thorfinn
The character known only as "Bug-Eyes Thorfinn" was recruited by the aging Leif Ericson as a substitute for the actual Thorfinn Karlsefni. Bug-Eyes plays a fairly small role in Vinland Saga and isn't the strongest Vinland Saga character, but he has his uses.
Later in the manga, Bug-Eyes Thorfinn was invited to Thorfinn's long-awaited trip to the New World, where he helped keep the voyage on track. However, he also tends to gamble too much and is rather irresponsible when left on his own.
17 Hilde
Hilde is a quiet, focused inventor whose life was turned upside down after Askeladd's band raided her town in Norway, and Thorfinn personally killed her father. Now Hilde burns for revenge, but she will also reluctantly help Thorfinn build Vinland.
Hilde isn't that strong, so she designed, built, and started using a custom crossbow that matched her strength. That wasn't Hilde's best invention, however, since she also built handy grain processing devices in the Vinland colony to feed everyone.
16 Ylva
Thorfinn's much older sister, Ylva, is largely a background character in Vinland Saga. She has considerable physical and mental strength alike, and after her mother became too frail for work, Ylva pushed herself to handle not just traditional women's work, but also men's work, such as fishing.
Everyone in Ylva's coastal Iceland town learned to respect the strong, reliable Ylva, and she can handle any labor-intensive chore for the sake of her family and community. Unlike most Vinland Saga characters, Ylva views strength in a constructive light, using her hands to make things and help people, not to kill.
15 Halfdan
Halfdan is a stern, unforgiving landowner and slave owner on Iceland's coast. He was introduced early on to set the tone of a brutal and unfair medieval world where people could be bought and sold, and iron chains represented people's bonds of obligation to one another.
Halfdan isn't a musclebound raider like Bjorn or Garm, but he is still a physically fit man at any age who use his trademark chains to attack or torture people. It must take considerable strength and skill to casually fling heavy metal chains around like that, and in his old age, Halfdan is still adept at this fighting style.
14 Fox
Fox, known as Kitsune in the original Japanese version, is one of several warriors who guards Ketil's farm in Vinland Saga Season 2. Fox isn't an elite warrior, but he has serious skills and experience as a swordsman, and he taught Olmar a hard lesson about having a strong will.
Fox rarely used his full strength in Vinland Saga. He was more interested in goofing off with the other guards, such as drinking or chatting the day away. He also sees very little in human life, speaking and acting casually about killing people with swords, much to Einar's horror.
13 Ketil
Ketil owns and runs his own farm in Denmark, a successful and peaceful farm with many slaves, farmhands, and sword-slinging guards. Ketil has left war behind and is now more interested in business, a lifestyle that neither of his warlike sons is too keen on.
Ketil has moderate strength for a medieval man of his age, and while he can handle himself in a fight, he'd rather not have any conflict come to blows. This, too, is a source of contention between Ketil and his sons Thorgil and Olmar.
12 Thorfinn Karlsefni
The bitter antihero Thorfinn Karsefni relied much more on speed and agility than brute strength to fight during his days as Askeladd's protege, and he pressed that advantage against the slower, stronger Thorkell. Now, after spending years on Ketil's farm, Thorfinn is much stronger.
Even if Thorfinn isn't a bone-crushing warrior like Thorgil or Bjorn, Thorfinn has some serious muscle after helping Einer spend months clearing out those trees to make a wheat field. Most importantly, though, Thorfinn uses that strength to build things and protect people, not seek glory on the battlefield.
11 Garm
The elite warrior Garm ranks among Vinland Saga's most talented and passionate warriors, even if he only has moderate physical strength by Viking Age standards. Garm relies more on skill and agility than brute strength to slay his foes, though fighting so often is still a great workout.
With his rigorous lifestyle, Garm has developed a lean but tough physique, and he can easily drive his unique spear deep into an enemy's chest and keep fighting without getting tired. All that, combined with his skill and agility, makes him deadly for anyone to face, even Thorfinn.
10 Askeladd
The antihero Askeladd shines most as a tactician and leader rather than a brute strength warrior, but he's not all brains and no brawn. Askeladd is one of Vinland Saga's most balanced characters, an effective mix of charismatic leadership, strategic skills, swordplay, and physical fitness.
Askeladd could never beat Thors or Thorkell in an arm wrestling match, but he's strong enough to knock swords right out of most opponents' hands and keep fighting with great stamina. This moderate strength, paired with his hard-won skill, makes Askeladd a fearsome opponent.
9 Snake
Snake is one of Ketil's guards on his Danish farm, but unlike troublemakers like Fox, Snake takes his duties seriously and is tough but fair. Snake wasn't quite a father figure to Thorfinn, but he did protect Thorfinn from Fox's bullying, and he was definitely more skilled than Fox was.
Snake is said to be somewhat stronger than Askeladd, which says a lot, given Askeladd's formidable strength and stamina in battle. On most days, though, Snake seems like a disgruntled slacker, which might give people the wrong impression about how capable he really is.
8 Floki
Floki is a Jomsviking officer, making him one of medieval Europe's most skilled and influential warriors of all. The Jomsvikings all have a well-earned reputation for their formidable skills, strength, and discipline as soldier-like warriors who fight in unison.
Rarely is Floki seen fighting anyone personally in Vinland Saga, but given his bulk and his role as a Jomsviking officer, he is no doubt quite powerful. He could definitely give warriors like Garm and Askelad a run for their money, though he'd rather send his troops to fight in his stead.
7 Ragnar
Ragnar appeared briefly in Vinland Saga as Prince Canute's loyal bodyguard, and he took that duty quite seriously. Ragnar wasn't Vinland Saga's most elite warrior of all, but his commitment to his duty and his natural toughness were both commendable.
Ragnar survived several battles while he and Canute were under Askeladd's protection, and he could hold his own in battle. Tragically, Ragnar was eventually killed, and the dandere Canute was grief-stricken about his fallen guardian.
6 Einar
After Askeladd's death, Thorfinn ended up a slave farmhand on Ketil's farm in Denmark. After a few years there, he met a new slave named Einar, who was captured in England after his mother and beloved little sister were killed.
Einar felt overwhelmed at first, as expected, but then he got used to the work and worked his way to his freedom. He used his impressive strength to chop down trees and remove their stumps, allowing him and Thorfinn to create a wheat field and sell their crop yields.
5 Bjorn
Askeladd's most loyal warrior and right-hand man, Bjorn, is a brawny and imposing Viking in any battle. Bjorn is highly skilled and durable, allowing him to survive many battles against other Vikings or English warriors.
Bjorn is quite powerful and tough already, but then he can go into berserker mode and double it. After eating a special mushroom, Bjorn will Hulk out and become a wild beast in battle, one that can even keep standing after a few hits from Thors Snorresson himself.
4 Thorgil
Ketil's younger son Olmar is all talk, and he can't even bring himself to strike an unarmed slave, nor should he. Meanwhile, Olmar's thuggish older brother, Thorgil, is a huge and tough young man who identifies strongly with the warrior lifestyle, similar to Thorkell, Garm, and Bjorn.
Thorgil often disturbs his father with his "might makes right" attitude and selfish ways, but it's not easy to prove him wrong. If anyone crosses Thorgil, they'll have a fight on their hands, with or without a weapon, Thorgil can overpower almost anyone and enjoy it.
3 Cordelia
At one point, Thorfinn met a brawny woman named Cordelia who, despite her size, was actually timid and kind as a gentle giant. She is Thorkell's child but doesn't like how she takes after her brutish warrior father. Instead, she was much closer to her mother.
Cordelia was once a slave, but then gained her freedom and gladly joined Thorfinn's Vinland expedition. She excels at manual labor with her formidable physical strength, proving that strength is better used to make things than to destroy them.
2 Thors Snorresson
Thorfinn's beloved father Thors was once famed as the "Troll of Jom," a Jomsviking with almost supernatural strength and skill, like a troll of Norse myth. Thors grew weary of battle and gave up all his Jomsviking glory to raise a family on the Icelandic coast, where he taught his son to never seek war.
Thors proved his immense strength when he faced dozens of Askeladd's men unarmed in the Faroe Islands. He fought them all off with his fists, which was both an impressive and bloodless way to fend off his enemies. And when armed with a sword or ax, Thors is unbeatable in single combat.
1 Thorkell
Thorkell can't quite match Thors in sheer skill, and he has actually lost to Thors before. Still, Thorkell is Vinland Saga's most physically powerful character of all, a titan of war who can seize a hefty log and throw it at the enemy from dozens of meters away. Not even a whole crew of ordinary men working together could do that.
Thorkell's bone-crushing strength and sheer love of violence make him a terrifying foe in battle. He is a whirlwind of axes, slicing and tossing aside countless armored soldiers with impunity. In fact, Thorkell is concerned that no one in medieval Europe can properly challenge him, so he was happy when Thorfinn proved a worthy challenger.