Shungiku Koikawa

A man covered in scars known as the "Killer of 99", Shungiku is a convict murderer who joins Mushibugyō in an act of repentance. The son of a bandit, he tried to avoid a life of crime until his mother is murdered, and blaming his father for it, he slays his gang and everyone else in his way in a killing frenzy that ends with his father's death, just to later know that she died by the hands of a member of Mushikari. Since then he looks for the man responsible for her death to avenge her.

[Spoiler] After finally avenging his mother, Shungiku changes his title to "Killer of 100". [/Spoiler]

(Source: Wikipedia)