naruto's punch were filled with kyubi's chakra and when he hit the kaiten with that punch all the chakra was relaesed and damaged both neji and naruto. naruto had the energy to do a clone and kick neji. in that fight both of them were damaged enough so that one punch could take them out. do not underestimate the power of kyubi. in the spiderguy fight neji just got some webkunai's in his back, that nothing like being hurt all over your body by chakra. you cant even compare these fights since neji probably trained alot and the spiderguy is nothing like naruto.