will we ever see the two of them fight?

I mean clearly they wouldn't be afraid of eachother, but in a room where people were afraid who would be stronger? would it be like the Thing vs the Hulk?

of course, this is if Peter only could use this ability.

Peter will have Knox's power, plus all the rest. Besides we haven't seen, yet, that Knox can be any stronger than Nikki, whose strength Peter already has.

I definitely agree with you here. I really don't see why knox is given this huge impression of being this gigantic amazing unstoppable powerful force that with his one power that is actually dependent on something, he's considered a match for peter and/or sylar and their plethora of powers.

It might be another thing if he could actually manipulate the emotion of fear, but obviously that's not what goes on.

If Peter used his powers with any reasonable degree of competence, Knox would stand no chance.

yes, and if peter could combine nikki's power with knox's power that would be a pretty painful punch

i think that knox's power could be overwhelming for peter and id like to see him use it against knox himself, which would result in a great scene