Lethal Risus
I have long been bothered by the inability of Risus to model one-hit kills or knock-outs in combat, so I came up with this house rule to address the situation. This is a simple house rule that you can use to inject some verisimilitude into your Risus games (if you must).

One Hit and You're Out!

In combat, if either side ever generates a roll result total greater than double the roll result generated by their opponent, said opponent must make a check versus a Target Number of 10 (using their current combat cliche) or immediately be taken out of the action. Whether this means death or unconsciousness is left up to GM judgement and the exact circumstances of the combat.

Other Uses

Although intended primarily for physical combat, this rule can also be applied to social encounters or opposed mental challenges. For example, this rule models the often instantaneous nature of failure in Shadowrun's mental Matrix combat.