With 14 Beast Marks, the Corrupted Beast was on the lower end of Infant Beasts. However, the sheer absurdity and abstract nature of its power boosted its danger several fold, placing it beside a regular, low Novice Beast.
But even that was too low of a classification, as regular Novice Beasts could be understood.
Taking countermeasures against a Light Beast or a Dark beast was not difficult, as research had been conducted for thousands of years to produce the most efficient ways of dealing with them. It was common knowledge.
However, due to the sheer rarity of the Corrupted Beasts, it was difficult to pin-point their weakness, if they even had one.
But, although the Corrupted Beast before Arthur had intelligence, it couldn't respond using human language, which indicated a lack of communication skills. However, that might solely be due to its infancy stage.
The Corrupted Beast hadn't fully developed, couldn't yet communicate.