Killing, deceiving, or misleading someone's mind (soul) by driving him to insanity or mindless wasteland (by preaching a fake religious doctrine or faith) is the worst of all the karma you can inflict on yourself. - Edward Rim

Driving someone to insanity is a much more serious crime than murdering someone, so the worst of all karma.

Why do I say this? Because insanity murders the mind (soul) along with killing the body by making it useless or purposeless.