Hulk took a hammer shot to the chest and barely moved. That alone is significantly more impressive than KC's moment. A charged Mjolnir shot, is way more powerful than Marvel Hercules, especially Heracles from DC. Throw in Marvel Hercules', and it becomes a pretty crazy feat. Especially since 2 issues later, Hercules and Jane Thor were holding up Earth....
That being said, the KC moment is more impressive in that it's a much better written scene imo, and is more badass. Just in terms of sheer power scaling, it's obviously no contest though.