Skill in the skill tree, know two handed has it, not sure about one handed. It's a random chance, usually the final guy you fight in an area, goes into a brief cinematic and pop goes their head.
Knocking people's heads offwith a warhammer is serious business. Your character stuns them with the handle, then does a mighty over-hand swing and somehow cleanly severs their head from the body. Barbarian surgeon secret.
Knocking people's heads offwith a warhammer is serious business. Your character stuns them with the handle, then does a mighty over-hand swing and somehow cleanly severs their head from the body. Barbarian surgeon secret.
Someone more familiar with the exact game mechanics may know, but I think they happen if you finish the foe off with a critical hit. At least it seems that way to me.
What usually works rather well is ... Several shield bashes with higher tier enemies, and then power attack with one handed. or Shield bash crirical power attack on lower tier.