New 52 khan hasn't appeared much. He steamrolled through new52 Shazam. He also had the anti-life equation and brought back the Old Gods in a fight with darkseid and highfather
We're using Fear Itself Serpent not the weakling shown in that flashback. It was confirmed several times during the arc that peak Serpent (empowered by enough fear) is more powerful than Odin. In fact, this is what was stated in the same scan from which Zack's cropped scan comes from:
Wrong. It required Kid Loki to actually warp reality (with Twilight's shadow) to implant a weakness in Serpent's history so that Thor, wielding the Odin-sword, could defeat him. This was stated in a later story arc and not in the original series iirc, either that or in a tie in, so i can understand the confusion.
On top of that, in the Fear Itself: The Fearless series, Serpent was revealed to have a Destroyer of his own which he created (the hammers merge and create him) who was at least on the same level as Odin's Destroyer. The serpent was also consistently stated to be far above any fear/hell lords, heck even his lackeys the Dumar were previously shown to be far below Hela in her own realm in a previous New Mutants arc. In a later story it was also shown that in a potential future, Mephisto in possession of Serpent's crown (made up of Serpent's fear power) would be able to conquer all the hell realms. And the fear lords believed that with enough fear power the Serpent will be able to crush the cosmos.
Yuga isn't winning this by any means, much less a stomp.