Like Max said, it's not the stats that make the legend. It's that something beyond the stats... Imagination. Creativity. the things that can't be quantified on a piece of paper.
Yes, you can build characters who can take on Fastjack in a fair fight. The thing is, you never would get that fair fight. He'd always be manipulating the situation to best suit HIS needs. You're more powerful than him? Congrats. Have fun facing the Agent Smith Army he's sending after your head. You're sneakier than he is? Awesome. Follow the trail into that node and enjoy trying to escape after he brings it down on your head. THAT is Legendary. That is why he's unbeatable. THAT is why he's unstatable.
Yes, you can build characters who can take on Fastjack in a fair fight. The thing is, you never would get that fair fight. He'd always be manipulating the situation to best suit HIS needs. You're more powerful than him? Congrats. Have fun facing the Agent Smith Army he's sending after your head. You're sneakier than he is? Awesome. Follow the trail into that node and enjoy trying to escape after he brings it down on your head. THAT is Legendary. That is why he's unbeatable. THAT is why he's unstatable.
That's the question, though. Short of directly fighting an AI, Fastjack has never been beaten in a fair fight that we know of.
The question is also one of SR4 otaku vs Fastjack. People keep saying that, with enough karma, an otaku plus sprites and threading will dominate any decker. But where will that same decker be, once he's got the same amount of karma? We know what Fastjack will be like: he'll have 7's in all his appropriate skills and needed attributes, a legendary Response 7 chipset in an amazing modified commlink (and will have the processor from a Mac Firestorm operating the digital clock), insane programs, and so on and so forth. But how much karma will it take to get him to the point of 7's in all the needed skills? To be able to build that amazing modernized cyberdeck, and code all his own programs?
Once we know a karma total, we can make the comparison, and see if the new otaku can really keep up.