Question

He is one of the most intelligent person in the
group (change the degree)​

Answer 1

He is one of the most intelligent person in the group (change the degree)

Answer;

He is more intelligent than many other person in the group.

Answer 2

Answer:

Very few persons in the group are as intelligent as he is. (positive degree)

or

He is more intelligent than most other persons in the group. (comparative degree)

Explanation:

The given sentence belongs to ONE OF THE case, that is the subject is referred to be ONE OF THE persons in the group, who is intelligent, just like some other persons in the group... So you need to begin the Positive degree with VERY FEW, always. And for comparative degree, the sentence will end with MOST OF THE... (used for referring to living beings) / MANY OF THE... (used for referring to non living things) .

Please do go through the explanation for a better conceptual clarity, which is very much necessary for English Language.

Hope it helps!