Fromund had always been physically stronger than most Phantoms. There had been no exceptions to this rule so far, unless his opponent was a Phantom of the same level as him. Even Adam had to admit this.
If their energy levels and mastery were the same, and they fought using only the strength of their bodies and fists, Adam would not stand a chance against Fromund. Some Phantoms, like Katrin, were not even worth comparing to Fromund in this regard; the difference was enormous.
There were many reasons for this, from Fromund's strong body to his abilities, the battles he had fought, and the decisions he had made on his path. But, as with any other Phantom, his Initial Gene had a strong influence on this, and his Initial Order only amplified this trait to the extreme.
For a K4 Phantom, destroying a Black Threat monster with a single punch was practically impossible.