Strategy against Nasus?
I'm not much of a toplaner and this isn't even about fighting him top lane. I'm actually asking about after the laning faze and for other lanes like mid or support. At that point hes got a pretty good amount of stacks fed or not is pretty tanky and hurts like a truck what do I do? Just run away, cant' that won't win games, cant charge him what do i do?

and try to destroy him. Even if you do destroy him he might get strong by stacking his Q when you are actualy being usefull and winning teamfights with your team, so you have to finish as quick as you can before he gets stacks. If he does he can change the course of the game by himself.