What is the most dystopian AH work ever created?

What Madness Is This by Napoleon53? It's basically Warhammer 40,000 levels of grim dark, where all or almost all the countries or factions are some degree of bad to worse.
Probably the Atlantropa Articles, by Cody Franklin.

There's this, but it's so extremely unrealistic it can barely be classified as AH in the first place.
You're right, that's not alternate history. That is a experiment in 'how unbelievably and cartoonishly evil can we make a regime that was already unbelievably evil for the time period it existed in'?"
I'd also have to go with For All Time. Nukes are dropped with reckless abandon, civil wars happen on a daily basis, 90% of the world is dominated by insane dictators and a handful of democracies which typically get destroyed, the Soviet Union gains so much more extra ground and there's a lot more places which fall to communist revolutions, which isn't helped by the United States returning to isolationism and sticking its head resolutely back in the sand, and American race relations just get worse and worse. That's just the tip of the iceberg.
I'll put it to you this way: Canada is paranoid and militaristic enough to have its own nuclear program.
Ad Astra per Aspera involves ASB elements like super-intelligent AIs and doesn't really go into the pre-Collapse history much.
If we exclude said Norden novel, then I would argue that said Orwell novel has to be excluded on the same basis.
Well, you could argue the whole ”Oceania is just Britain” thing. But yeah, in terms of AH.com timelines, WMiT Redux ranks at least in the top 10
Big Brother might not have actually controlled 1/3 of the world. For all we know, the propaganda outlets might be lying about that, and Ingsoc only controls Britain and tells its citizens that it controls more.
...so? That was not why I suggested it not to be a candidate, I was speaking strictly from a Doylist perspective of it not being meant to be taken as a realistic depiction of human society, just like the Norden novel mentioned by the OP.
The most dystopian I've ever read was NSA by Andreas Eschbach.

Basically the III. Reich in a Babbage-Punk scenario, with complete control over (social) media, only electronic currency and people just learning how to use that stuff.
Especially evil is a popular diary-app.
For All Time explores so many different types for horror and with such a darkly humorous tone, that even if it's not the most dystopic in liters of blood spilled uselessly I still think it's pretty good at showing the death of concepts-- of diplomacy, of restraint, and finally of governance itself.
The Draka series?
Guess we have a winner here, given that it does, well, end up with America being turned into a safari where humans are hunted for sport by the genetically-enhanced master race that rules over Earth with the help of its population of slaves made biologically incapable of revolution.