I'm gonna do a r/theydidthemath moment.
From a online description, it is a 12 ft tall (3.6576 m) giant skeleton.
That is 1.34 time taller than Robert Wadlow (2.72 m - 8 ft 11.1 in), the tallest man ever recorded.
If you wanna know the mass of this thing. (If we assume it's a real human's skeleton for fun)
A human's skeleton accounts for approximately 15% of their total body weight.
The global average human's skeleton weighs approximately 9.3 kg and the global average height is 1.6525 m.
Using square cube law : (3.6576m/1.6525 m)*9.3kg = 20.58 kg. (For the skeleton)
So the whole body mass should be : 137.22 kg. (/0.15)
To verify it. We can use square cube law with the average global weight: 62kg / 136 lbs.
(3.6576m/1.6525m)*62kg = 137.22 kg. Match perfectly.
The average KE of a good punch is 70 J (from a non-boxer person).
So : (3.6576m/1.6525m)*70J = 154.93 J
Using the mass : 154.92 J (still match)
Using the inverted kinetic energy formula :
This puts the speed of the Skeleton punch at : 16.79 m/s.
For it's sprinting speed (assuming it can sprint), the average human sprinting speed is 6.35 m/s
So using square cube law formula, that is 14.05 m/s.
As a point of reference: 18,228 J is the energy equal to a fall from 30 meters high which is considered 100% fatal if the impact is direct. But a lot of blunt impact, demanding far less energy can kill from with about 100 J. (if it hits more sensitive places)
[And by the way, to "Kill it"]
The volume of our Skeleton is 20,580 cm³.
Human bones has a tensile strength of 150MPa, a strain to failure of 2% and a fracture toughness of 4MPa(m)½.
Here I am going to assume destroying the entire skeleton with a single attack, not a specific bone or a single part with these values. (So not 100% accurate)
So if it ran into you at full speed, it will fracture bones. That match the giant we got in real life that couldn't stand nor walk without a cane.
So yes, a Boss that looks impressive but isn't that strong overall. You can literally lift it up and drop it in a river.