In the latest episode 85, the catgirl(boy?) easily killed Kite even though Killua said Kite is as strong or stronger than a Nen Master. I thought chimera ants were made from normal no nen 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:
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 the cat girl.