Nasus is a champion played exclusively by a select few of us in the community. If you come against one then you most likely are not going to win the lane. This does not mean he's busted but that you are against someone who took the time to master him and main him through his ups and downs and knows how to play around his weakness's and still do well. However like you in this scenario Nasus will be dependent on his team doing well. You may lose lane against him eventually but if your team dominated then there will be little he can do as he no longer can carry do to the inanely free amount of damage in the game now. However if his team did moderately well and you could not shut him down then he will be a massive issue if your team is not more coordinated than the Nasus team.
Nasus is a mid/late game dueler who excels at 1v1 and 1v2. If you are fighting him when he's legit strong in these situations then you are playing to his advantage and not yours and will just end up making him stronger. His whole kit is predicated on one damage ability which is why he is remains balanced for the most part. He doesn't have tons of early damage, no instant mobility and hard CC like so many others like Fiora, Riven, Ekko and Jax just to name a few. There are other champs who are legit abusive in their current forms but Nasus is not one of them.