So, as I was watching Vinland saga and saw the profiles in less than optimal condition, I noticed something
Thorkell is very good at throwing spears
Then I noticed later that it was already calced but I'm not entirely sure about their methods so I'll do my own thing
Let's assume that the thin lines we see at the edge of the horizon (note: likely not actually 4.8 KM away) are pikes that aren't at the right angle to shine from the distance, with pikes being anywhere from 3 to 5 meters. These seem more on the 3 meter end judging by the pictures. And, since the perspective is a bit behind Askeladd and co, I'll anglesize how far his head is from the camera. He's 1.7 meters, human head is usually 7.5 times smaller, thereby making it 0.227 meters
The pikes are like 3 pixels at most, the panel is 584 pixels, and Askeladd's head is 8 pixels
For anglesizing, the formula is 2*atan(tan(70/2 deg)*(object height/panel height)), which in this case would be 2*atan(tan(70/2 deg)*(2/584)) and 2*atan(tan(70/2 deg)*(8/584)), which is 0.00479593285 and 0.0191831799 Radians. To convert to degrees, it's rads*180/π, so, 0.00479593285*180/π and 0.0191831799*180/π makes for 0.27478671113 and 1.09911524591 Degrees.
Putting all that into the anglesize calculator makes Thorkell 625.53 meters from the screen and Askeladd 11.833 meters from the screen, 625.53 minus 11.833 means Thorkell chucked the thing 613.697 meters, as a final distance. Wew.
The anime is really faithful, so I'll use it's timeframe of 3 seconds here. The panel composition on the manga makes it seem instant, with how it jumps from the throw directly into the guys being impaled, but 3 seconds is still really fast for a spear to be thrown in this situation. Maybe I could make a high end with one second.
613.697 divided by 3 is a speed of 204.565666667 meters per second, divided by 1 is just 613.697 meters per second
Now, I'm actually kinda okay with the way they got mass, so .5 times 4.786 times 204.565666667^2 and 613.697^2 is...
Low End: 100140.138966 Joules, Wall level
High End: 901261.250687 Joules, Wall level
Now, of course, this also requires some force, but trust me, you don't want to see that. It's nothing but depression.
Now if only the angle on him tossing a rock at people wasn't so screwed up I couldn't do anything with it