The thing that bothers me the most about Nasus is his W. I am okay with his Q dealing fucktons of damage, the problem is that his W makes me unable to escape for the most part, the slow is too strong and the attack speed slow also prevents me from dueling Nasus if I am an attack speed focused champion, so not only I am unable to escape from Nasus, I can't even fight him back.
Look at Darius. He deals so much damage. But unless you get caught by his E, you can avoid his damage. Even if you get caught, you can still have a chance to escape if you use mobility spells or slow Darius. And even if you can't escape at all, it is still possible to duel Darius, depending of the champion you are using. But Nasus? Your only chance is to dash on the other side of a wall, since you will not escape from him otherwise (and even then, Nasus can use Flash himself, provided he carries this spell). The attack speed slow prevents you from dueling Nasus, unless you can QSS it (and even then, Nasus' W has a really low cooldown).
This ability also makes Nasus one of the best champions in the game when it comes to setup ganks for his jungler. If the enemy jungler is nearby, unless you are close to your tower, you will not escape the gank (and even then, between Nasus' ult and towers being weak overall, it is not like he can't dive you regardless).
On my opinion, Nasus' W is one of the worst designed abilities in the game. It has very little counterplay. People complain about Malzahar's ult, but Nasus' W is almost on Malzahar ult's levels of retarded. While it isn't a suppresion, it makes up for that fact by being a basic ability with a low cooldown instead of being his ultimate.
