Gon, Killua, Chrollo, Netero, Tserriednich. We know them all to be extremely talented Nen users who grew at an exceptional rate. For a long time it bothered me Tserridnich grew in Nen potency at such an advanced rate, when no one else in the series had, until I realized it was consistent with what we've seen the entire time. Every high potential nen user was already amazing before they were introduced to Nen.

Gon grew up as a forest child. His eyes and nose adapted to the wilds of Whale Island giving him a level of perception most humans don't have. He captured a giant fish several grown men couldn't touch, at 12 years old. As well as amazing athletic ability, quick adaptability, and a strong sense of survival. Even without Nen, he got a lot of attention as someone special at the Hunter exams.

Killua has been cited as the most naturally gifted of the  Zoldyck's in term of assassination ability. He got all the way to the 200th floor of Heaven's Arena when he was 7. We saw him take out a serial killer before we even knew about Nen. He was even such a great assassin that he learned how to walk without making footsteps. He was a force to reckon with even as a child without Nen, Nen just helped get closer to his maximum potential.

Netero, we saw his journey to being incredible. He perfected his martial arts to the point of his punches being faster than sound. There were no martial art opponents, who lacked Nen, that could touch him. And he used dedicate much time to prayer and practicing inner peace. He was a monster before Nen and Nen only made that 100 times amplified.

Chrollo, we saw his potential in a different way. As a small child, he understood the intricacies of dubbing a series into another language, using multiple voices to distinguish characters, how to rewrite a script for another language, and the difference in the needs of a dub and a live show. These are pretty advanced concepts for a 9 year old to grasp, yet he did anyways with no training. He was already a genius before he knew anything about Nen. Give him a power that grows exceptionally if you're intelligent and clever and well...We see what Chrollo is made of.

This brings me to Tserridnich. He is highly intelligent and cultured, as well as having the pride of being a Prince. You give someone like that access to something like Nen, with teachers who can help him grow as quickly as possible, he's going to quickly understand and get the nuances of the concept, even after a short while. Not only is he talented, he's a grown man in the peak of his physical health, which only helps him grow in Nen skill exceptionally fast.

All of these characters have been shown to be monsters before they knew about Nen. Far above the capabilities of most human characters in terms of power, intellect, or both. Nen is an extension of your sense of self and anyone with a high amount of intelligence, power, and charisma, will quickly grow in Nen.

I could also talk about Ging being the same way, but I think I've made my point already. I think it's so cool this has been consistent, and it's another reason I love Hunter x Hunter.