It's in the complete adventurer.
Smite the Guilty (Su): Starting at 2nd level, a vigilante can attempt to smite someone whom he has personally
witnessed committing a crime in his home city. He can use this ability once per day. He adds his Charisma bonus (if any) to his melee attack roll and deals an extra 1 point of damage per vigilante level.
The smite attack must occur within three days of the crime; otherwise, the benefits of this ability no longer apply. A vigilante can use this ability multiple times against the same miscreant and in response to the same incident, so long as all such uses occur within the time limit. Should a vigilante mistakenly try to punish someone who is not guilty of the crime witnessed, the benefits do not apply, but the attempt still counts against the number allowed per day.A vigilante can use this ability twice per day at 6th
level and three times per day at 10th level.
I'm considering just going Iaijutsu master from Oriental, if it's allowed