Why are the royal guards so powerful? In the latest episode 85, Pitou easily killed Kite even though Killua said Kite is as strong or stronger than a Nen Master.  I thought chimera ants had nen similar to that of humans.  How come they are so strong?
Before the royal guard was born, the chimera ants became aware of humans with 'excessive life force' (a.k.a. nen) and the queen ordered them to hunt down any nen users that were in the area for her consumption. We know that there were hunters in the country at the time, like Ponzu and Pokkle's group etc. We can assume that the queen consumed these hunters and the royal guard inherited the nen abilities. 

The rest of the chimera ants are receiving (as of episode 85) their nen abilities the regular way - through the "baptism" which awakens nen in a person. This is how most humans acquire nen abilities, as was probably the case with Kite. 

The overwhelming strength of the royal guard can be attributed to:


They are born able to use nen, unlike human most nen users who are "baptised". This gives them an advantage because their understanding and ability to use nen is innate, not learned through years of training and study. 
Chimera ants are insects by nature and are usually brutal, savage, and cruel. This leads to more menacing battle auras, which can hinder the fighting ability of a human opponent if the aura is intimidating enough. For example, Pitou's aura was menacing enough to scare away Gon and Killua. 
Chimera ants also have the properties of any animals or humans that were eaten. This means that any member of the royal guard is going to have incredibly fast animal-like reflexes, the intelligence of the best humans, and the strongest muscles between animals/humans.


The combination of these means that the royal guard is going to be significantly stronger than most average hunters. 

Kite was also at a disadvantage because he lost his arm protecting Gon and Killua before he fought Pitou.