If sion is a hyperscaling tank, why does his winrate drop massively the longer a game goes?

How on earth does malphite get extra damage when building armor? i think u meant rammus or Taric. Malphite gets more armor when he builds armor.

Nasus doesn't worry about using his Stacks on an enemy. Nasus worries about Three-shotting a turret, while his team plays 'Catch me if you can' with the enemy team

Honestly, the best advice I can give is to ask your jungler for help early. Nasus lanes tend to draw focus from both junglers (Wither is great for setting up ganks while Nasus is an easy target early-game).

One of the most important factors is wave-control. Whenever I play Nasus, I always try to freeze the wave just outside my tower since it makes it difficult for many opponents to harass me, can make me difficult to gank without a risky tower-dive, and leaves my enemy over-extended and exposed to ganks.

Against Nasus, you want to get the minion wave on your side of the lane and freeze it. Nasus has no mobility and his only ranged attack has a high mana-cost, so this can let you chunk him for every CS he goes for and deny him the opportunity to sustain. It also makes it easy for your jungler and/or mid-laner to gank him and harder for you to get ganks.

I generally recommend playing durable, high-damage champions against Nasus. While some squishy champions can make his life horrible early, he will generally murder them with 200 stacks and Sheen (roughly 10 minutes into the game). Nasus can't effectively itemize penetration without sacrificing durability, so champions who can stack armor and MR mitigate his damage greatly.

The following champions are quite good at dealing with Nasus (in my experience):

This is my default counter-pick to Nasus. You quickly become unkillable and your mixed sustained damage will gradually eat through him. I typically manage to first-blood Nasus at level 2 without jungler intervention as Mundo and snowball off of that.

These champions can build Black Cleaver into defensive items (i.e. DMP, Sunfire Cape) to trade with Nasus. They are strong early-game, have innate sustain and they can trade favourably with Nasus so long as they can control the minion wave. In addition, Wither doesn't effect them too badly.

While Wither can cut your damage out-put, Trundle's early-trade potential and sustain can let you build a lead against Nasus. Late-game, Trundle can crush Nasus in a 1v1 fight (so long as you have QSS for Wither) and his ultimate will make Nasus squishy during teamfights (while making Trundle unkillable). I'd probably recommend Blade of the Ruined King -> Sunfire Cape in this match-up. Also, Trundle can solo buff camps at level 1, so I'd recommend stealing the enemy red or blue buff and then teleport to lane after basing; you will have an experience advantage and the minion wave will be pushing towards your tower.

can be a painful match-up as Nasus. While you are both rather weak early-game, you both scale extremely well and Vlad has the range advantage. Vladimir is one of the few match-ups who can constantly harass Nasus under-tower and out-sustain him. Once Vladimir has Hextech Revolver, Rylai's Crystal Scepter and Void Staff, it can be very difficult to deal with him (especially if he has Boots of Swiftness to kite you).

Champions in other lanes are quite capable of countering Nasus too.

can kite and murder Nasus at pretty much every stage of the game if he has his ultimate. If he builds appropriately (i.e. Rod of Ages, Rylai's Crystal Scepter, Liandry's Torment, Void Staff), he can even wean Nasus down without it due to his high damage and durability.

is capable of dueling Nasus whenever he has his ultimate available. Highlander makes Master Yi immune to attack speed and movement speed slows, which renders Wither (Nasus' main defensive tool) useless. Master Yi will typically be able to kill Nasus through raw DPS while Skirmisher's Sabre and Meditate can be used to reduce the damage Nasus deals to him.

are especially valuable against Nasus as most champion. In addition to providing armor, it reduces the damage of his Q and basic attacks by an unmitigateable 10%.

and and are very useful to have on your team against Nasus since they can help your team kite him during teamfights, preventing him from reaching or sticking to targets.

dont be scared to play the teemo. Its not a bad counter. Even if you lose lane, once you group you save the blind for when he gets close. It stops a chunk of his damage. AD is better at countering nasus, but AP works fine too.

Kennen plays similar to teemo but with more utility. A lot of autoattack harass.

Another option is to play heimerdinger. He does well in lane, then once you get a rylais its easy. You can basically kite him forever, both solo or in a fight.

Tryndle cant bully as hard, but taking away his takiness makes him easy to kill.

Fiora can 1v1 him most of the game. So can Pantheon. Darius and Morde do well too.

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Nasus is more mid-lategame, isn't he? Because after that point, pretty much everybody can kite him to hell and back.

Saying you can kite Nasus implies that Nasus is teamfighting.

And I don't know why he would ever do that.

One innately stacks Damage and the other innately stacks HP. The primary difference the Damage vs. Tankiness curve. Nasus gets Tanky early and then his Damage scales. Sion gets Damage early and then his Tankiness scales.

That said, their gameplay patterns are completely different anyway. It's like trying to compare AD and AP Nidalee. The difference in gameplay pattern is night and day regardless of any similarities in their kits.

Just as much as Liandry's. But Liandry's is problematic since it doesn't work on all champions.

Except he offers a lot in teamfights.

Kindred is an early game snowballing jungler. The infinitely stacking portion of her passive is only infinite in theory and naturally declines in usefulness as the game goes on since it's current %hp damage and not total %hp. But it does make her snowball harder off early leads and help her end the game before her short ranged kit with its limited usefulness steroid falls off a cliff. It's not a infinitely stacking passive because she's meant to scale super well; it's just infinitely scaling because there's no good reason to cap it.