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.
Thorfinn's sister Ylva also seems to have her fair share of fans, despite barely appearing.
Fan Nickname: It's not uncommon to hear people refer to post-timeskip Thorfinn as Viking Kurt Cobain due to his appearance.
Much like how in Code Geass Suzaku would have several nicknames with "something"-zaku, most of Canute's nicknames follow the same pattern. Earlier Canute is referred to a Moenute, after his Rage Against the Heavens he's Garnute, and more recently he's become Jerknute.
The first post-Time Skip arc is called "Farmland Saga."
Growing the Beard: Canute, and boy does he. Then he goes and grows an actual beard to complete the image.
Wangst: Thorfinn gets called on this by some critics, but at least he has a legitimate reason for his bouts of depression and general surliness, but Ketil's son? A spoiled little rich boy who wants to be a warrior, always whining about how life is unfair. Here's hoping Thorfinn gives him the beating of a lifetime.
The Woobie: .........come on, Canute? I mean how can he not be after his "My Father harbors no love for me" speech in chapter 42? Not to mention Ragnar's death before that.
Arneis. Arneis. Losing her husband because he went to fight a meaningless battle for no reason, followed by losing her son when she was made a slave. She's sold to Ketil, and seems to do well on the farm but at the cost of being Ketil's bedwarmer. Then her husband comes back as an insane criminal who wants to save her and recover their son. Then he dies in her arms and Ketil violently beats her into a bloody pulp when he gets the news she tried to run away at just the wrong time. Then she dies of her injuries, pregnant with Ketil's child.
Thorfinn, big time. To say why would essentially mean summarizing the entire series.