Honestly, when I think of Kratos and the Norse pantheon, I think they have a lot in common. Don't think of it as "Kratos vs some godly punks who are the Olympians but more mortal," think of it as "Kratos vs a large amount of people who are basically him but more so." The Greek and Norse gods alike were both very human, but the Greek ones were a bit more...I don't know what to call it. Unchallenged? Top-o-the-heap? God-cheesed? The Norse gods fought and tricked back and forth with their enemies all the time, but I can't recall the Olympians having any issues beyond bickering with each other past the Titans.
As an outgrowth of this, the example of "the Norse gods get old without the apples and they won't last forever" doesn't seem to make them appear wussy so much as highlight this. They're restricted and challenged by more stuff than the Olympians, and then they go out and do some pretty amazing things anyways. Does rowing out hundreds of miles to sea, disparaging the whales your fishing buddy's catching as small fry, using an ox's head to fish up the serpent that circles the world that's also fated to be your arch-nemesis and killer, then slinging your mountain-cracking weapon right at its skull sound like something Zeus would do... or Kratos?

Besides, the Norse gods all know they're going to die. How impressive is killing someone who was going to die anyways, just later down the road? There's no glory in deflating hubris there - they're neck deep in fatalism already.
"Decapitated by a madman with giant machete-chains? Well, I was going to get eaten by a wolf, and my son's set to drown in an ocean of venom...and...uh...I think a lot of the rest are going to go when the entire world gets set on fire. Oh, you killed that guy already? Weird, that wasn't supposed to happen."