Just go trade with him early game (ofc when his jungle isn't near), or else one would end up in this particular situation below.
http://www.troll.me/images/oh-lawd/what-is-nasus-q-stac.jpg
http://i159.photobucket.com/albums/t123/h0meles/macros/screaming%20catman/over9000.jpg
Spectating a friend's game "What are that Nasus's stacks at? Hmmm. Only 75 at 30 minutes, what is he doing?" [Nasus one-shots the enemy ADC] "... what even. How." [checks stacks again] "Ohhhhhh. It's 750. Neat."
Then the nasus decides to backdoor...
Ooooooooooooor you can just use Vladimir and out-poke him, out-trade him, out-farm him, out-scale him, and out-push him until their nexus explodes.
Edit: Good point, Nasus can scale infinitely... -shudders-
I don't try to deny Nasus anymore. Not worth the effort. So I just play
and do the same thing he does, but better.
+1 thanks for the laugh
basically just get 500 stacks then perma group with your team and auto kill the enemy carries naut support nasus top. ez win imo if you dont get creamed early game.
the idiots that leave lane when you have a nasus opposite you its a full game job to make sure he doesnt stack