i just can't see away to counter him now that he has the ability to completely ignore his major weakness which was his laming phase now because that fucking split push nasus build. the only way i know how to counter nasus is to pick a champ that can easily deny him farm. but now if that happens you can just switch from stacking mode to poking them to hell with an ability that is incredibly hard to dodge. what do i do?
split push nasus destroys his late game, he gains almost no stacks at all.
not to mention that even if he's stacked to high heaven it doesn't matter because he's hyper-kitable.
If only there was an item that rapes armor stacking champs and shafting their healing and an item that removes debuffs 
His major weakness is the fact that he cannot teamfight whatsoever and is very easily kited and focused down.
IMO take Renekton. You can adjust your playstyle quite easily depending on what he does.
If he chooses to Spirit Fire the wave, you can freeze the wave at your tower until his E starts really hurting.
When it does start dealing significant damage (around level 5) you should have enough gold to get a Tiamat; this will let you clear the wave just as fast as Nasus can.
After that, rush a Black Cleaver to extend the window that you can punish him through armor.
However, if he decides NOT to max Spirit Fire, then shove minions into his tower until he hits level 5. MAKE SURE YOU WARD.
After level 5, you need to manipulate the wave to freeze on your side of the lane. If he ever comes up to try and Q farm, go all in and try to kill him.
In this case, don't take Tiamat; it will prevent you from freezing the wave. It also delays your Cleaver, which is more significant since any good Nasus maxing Q would rush Frozen Heart in this matchup.
Also, make sure you ALWAYS take Frevor of Battle against Nasus; the extra % Armor Penetration you get from the Ferocity tree is very necessary when it comes to bullying him.
Pantheon.
Wouldn't Darius be a decent pick against Nasus? Only because armor stacking against Darius with BC is useless and at least you have some sustain if you hit him with your Q. Plus you can bring a little more relevancy to mid game than Nasus. Plus you could get Executioner's just to be a giant bitch. Bleed effect will keep it on him forever and make his Passive less effective.
all these champions counter his splitpush build AND his stacking build.
excutioners, buying a talisman yourself so you can collapse on him faster, learn how to gauge your damage so you can properly execute perfect kills (on him) without letting him realize your full nuke numbers. sounds easy right
I personally like new Yorick vs Nasus. He sustains well and does most of his damage through his minions. Last Nasus I fought I crushed with just making sure I constantly had minions up and hitting him with my E so he took % health dmg constantly. If you can get him inside your W with the Maiden up then it's GG for Nasus.
In truth though there are no true counters to Nasus as he can constantly scale and become relevant as long as his team can keep the game going.
As a Jungler I must say how annoying that Champion is to have in the game. If I don't camp the enemy Nasus till mid-late game he's just going to scale so hard. So that usually denies me from helping my bottom lane as much as I'd like because I have to show up to Top lane to push the Nasus back (either dead or at least back to base). So your Jungler plays an important role in helping you deny Nasus farm.
Lane bullies can usually prevent Nasus farm, if you can poke him a ton and freeze your lane then you should be golden.
Theres also items 
your carries can get to prevent the Pup from demolishing everyone in teamfights.
I would think 
is a good counter to him (like in general dont go tank eve top).Just w his w and stay in q range of him so he cant get you.
lulu is a great counter, at level 3 he can cast every (roughly) 12 seconds without CDR, you have the ability to shield yourself for that damage, + wimsickle your way out of a fight (and to top it off) if he gets to close polymorph his ass till your MS is restored :D (NOTE: poly will also deny him early crucial CS) (i'd also advise building thornmail, though... not as lulu)
