Suikotsu

Suikotsu was a member of the Band of Seven. He had two definite split personalities. One, a gentle, philanthropist doctor who looked after orphans; the other was a sadistic, Wolverine-wannabe killer that earned him a spot in the Seven-Man Army. When his evil side took hold he seemed to possess a dry sense of humour and a insatiable desire for blood, while when his good side was in control he often hallucinated that he had blood on his hands. He may have a third personality, as shown after he fell off a rope-bridge; this personality seemed to be a combination of his other two.

(Source: InuYasha Wikia)