My friend and me were arguing what was Pacino in Devil's Advocate?

My friends explanation:

"He wasn't the Devil, he was the guardian angel who wanted Kevin (Keanu Reeves) to do the right thing and quit the little girl case. Pacino (guardian angel) wanted to show him that if he chooses the wrong path , bad things will happen to him".

My explanation:
He was the Devil because in the end he said "Insanity is my favourite sin", if he was the guardian angel he wouldn't have said that.

What do you think, who is right? or if you have different explanation, you are welcome to explain.