This is the 8582nd most frequent Russian word.
одному
"Одному" means "to one person" or "alone" in English, depending on context.
In this sentence, "одному" is used in the dative case, referring to a male individual, indicating that the action described is beyond that individual's ability.
Одному человеку не под силу поднять такую тяжесть.
One person cannot lift such a heavy object by themselves.
Here, "по одному" is an idiomatic phrase meaning "one at a time," showing a sequential or individual approach.
Мне нужно поговорить с каждым из вас по одному.
I need to talk with each of you one at a time.
In this sentence, "одному" is used in the dative case, reflecting the state of being alone, correlating with the subject feeling fear in solitude.