Ness is from EarthBound. He's this kid who basically can beat the crap out of one of the most powerful RPG villains of all time who is nothing more than an incorporeal mass of energy with a plain old baseball bat. His psychic powers are also quite immense and Seph has no defense against that.
And you are quite right on the EU Jedi. As for demi-god, it's how I calll him. He may very well have been a god but I've simply gotten into the habit of calling him a demigod. Not many ultra-powerful beings are known as gods, actually from what I've seen. If a villain has tremendous power, people refer to them as demi-gods.