Here are some possibilities:
* "Devilish" - This word means "like the devil" or "evil," and is often used to describe something cunning, mischievous, or cruel. It's possible that "devil his" was a phonetic mishearing of "devilish."
* "The devil himself" - This phrase refers to the devil directly and is used to emphasize the evil or malicious nature of something.
* "Devil's Advocate" - This phrase describes someone who argues against a popular or generally accepted view, often to stimulate discussion or highlight potential problems. It's possible that "devil his" was a misunderstanding of this phrase.
If you can provide more context about where you heard "devil his," I might be able to give you a more accurate answer.