I did not want to post anything on here but I guess I will after all. I'm bored.
As people already said, I don't think there is anyone who is without a doubt best NW. There is an elite who can beat each other on different days. Nevertheless there are some people who just do it more consistently, they of course will lose too, but win more often. So the hardest adversary I have ever faced would be ClaSh for me. Naturally things really depends on styles, ping or lag in general and factors like having a good or bad day, but he just was a nightmare for my style and seldomly seemed to have bad days. I didn't duel him much, but when I did it was just hard as heck.
Cavalry I wouldn't know, never really pay attention to them nor play it.