I mean probably Marvel Zombies.

Zombies

What If…Ultron won?

That’s all I can think of that were dark

The supreme strange reality in “What if Doctor Strange lost his heart instead of his hands” is pretty dark but the “What If Ultron won” is the darkest

Strange Supreme's episode is what immediately came to mind, but others are the Emergence universe (the one where Riri dies), and Infinity Ultron's universe.

Infinity Ultron universe (Both of them but especially the Good Infinity Ultron universe in which nobody but Ultron is left.)

Strange Supreme Universe

Emergence Universe

The Zombies universe isn't really that bad at all when you come to think of it. It can easily be fixed, it might take forever and some heroes aren't coming back but there are more heroes alive in that universe then most of the other universes. All the Other universes pretty much all the Heroes are dead and gone lol.

That's... not an easy fix. Unless you call causing the Emergence fixing it.

@Xandermcc I think he means broadcasting the Mind Stone's frequency to all the zombies, which'll hopefully be the plot of Marvel Zombies.

The Avengers Assassinated universe.

@GarrettSMW Even if you ignore the Mind Stone Fix, they can survived the Zombie universe without fixing the zombies. If the Morons from Walking dead can survived it then the Remaining Avengers Heroes (One of them being Spider-Man) can do it as well.

All the other universes that was mentioned (except for the Dead Avengers universe) either have pretty much everyone but one person Dead (OG Infinity Ultron is just Nat, Good Infinity Ultron is literary just G.I.U, the Emergence universe is only a few people left and barely any heroes to protect them) or Everyone is dead (Strange Supreme). You're not fixing those universes at all.

^Even the Good Infinity Ultron universe has no inhabitants because Ultron died saving Captain Carter and Watcher.