Killing intent is different from sword intent. Sword Intent often needs to be improved by the improvement of perception and mood.And there is only one way to improve killing intent and that's by killing. Killing intent can affect other people’s minds, can make people lose their minds becoming a person that conciousness is only to kill. People who are crazy killers will be controlled by the killing intent and as long as the opponent has the killing intent and the strength of mind are weak these opponent will be controlled aswell.