Its somewhat of a tie between someone getting impaled straight through and getting a hole in their chest where their heart used to be (and their heart no longer being there). This was by the final boss. 

Or someone's face getting smashed brutally and bloodily into the pavement by a Romper.

EDIT: Both of which were either a Fumble on their dodge roll (when I rolled dodge instead of doing Static dodge) or a Critical on the enemy's attack roll.