There have been better pictures released since he was first revealed, but I'm lazy and this is what I'm offering.

And Ninja Prime would kick ass.
N. Prime really doesn't have much of a backstory either, truthfully... Hasbro/Takara creators were sitting around one day going "you know, we've got this kinda cool [laser] Prime sitting here and people seemed to really enjoy spending money to own it, but how do we get people to buy it again so that we can make more money without spending more money on new molds/retooling?"
Then guy two, probably making tiny birds outta consumer cash goes "Let's repaint it."
And guy three, bored with rolling up his tie, says "Into who, Prime's too distinct of character?"
Guy two, "Magnus!"
Guy one, "We already have RID Magnus."
Guy two, "Oh yeah..."
Guy three, "I've got it, Evil Prime" Making spread hand gesture.
Guy one, "Meh..."
Guy two, "No wait... Someone as tough as Prime, with all Prime's strengths and none of his weaknesses."
Guy one, getting into the idea, "...and we'll paint him... Black! Cause that's as evil as evil gets."
Guy four, up until this point quiet, "And that'll be good enough for the 1:30 meeting, let's get some lunch. We can work on a better name then." Though secretly, he's slightly offended by the black=bad association.
Guy three, as they leave for Arby's, "What's wrong with Evil Prime?"
For my money, if/when we get it Stateside it'll be rechristened Onslaught. At least he has a decent backstory.