Hard to answer because so far, Jor hasn't done much of anything but stand around and talk. If he wants something done, he has someone else do it for him. Yeah, there was that time he handled Lex but even then he didn't do much other than blast him with heat vision.
I'd say his most dangerous aspect is the fact he can seemingly teleport other beings, at will, into a prison cell he's prepared. But other than that, it's hard to say how dangerous he'd be to Marvel Earth and it's heroes.
Think of him as being Supermna, but mjuch smarter, better tech, and willing to do what needs to get done!