##Use a different (weaker) weapon.
Use a different (weaker) weapon.
In the example you used, Fighter McFighterson is trying to apply a poison. Just apply the poison to a dagger. That drops your damage from 2d6+9+2+1 down to 1d4+6.
That brings your average damage down from 19 to 8.5
P.S. - I specifically did not mention nonlethal damage or what I would do as a GM, as that has already been mentioned in other answers