Hackmaster has a "Threshold of Pain"; if you take more than that amount of damage in a single blow, you have to make a Trauma Save by rolling under 1/2 your Con on a d20p. If you fail (more than 1/2 your con), you are incapacitated for 5 seconds for every point you fail by.
It takes 10 seconds to Coup de Grace. It takes a multiclass thief 5 seconds; thieves can do it in 3, and assassins in 2.