You may view Friggzerker’s hesitation in a number of ways. You could see it as reluctance to kill someone she’s close to—that never stopped Byron or any other berserker once in full-bore berserk mode, but Frigg is fundamentally more stubborn. You could see it as foreshadowing for what happens later, an early sign that Frigg’s divinely granted powers and a berserker spirit don’t sit as well together as HR might have hoped. You could see it as the simple drive to level anything that’s standing, and right now HR’s standing and WAV isn’t.

Me, I think it’s this simple: HR is trying to boss Frigg, and nobody bosses Frigg. “Destined for defiance,” I believe the phrase was?

Last-panel HR is still pretty sure his power is sufficient to keep Frigg from damaging him, but he’s gonna trot to get a bit more distance from her, just to be on the safe side.