A raffi is a considerable dickhead. By dickhead the author means dick-head. He has a penis-shaped upperbody and his head looks like the tip of a dick. Not only is this physical but if someone is a dick just call them a raffi. Ra means dick and ffi means head in Armenian, Latvian, Canadian, and of course Martian.
That guys upper-physique make him look like a dickhead, ergo he is a raffi.