I've conferred with Lenny and with Clark. The Victor example is wrong -- it's based on an earlier version of a spell that was shown in the text before the example spells, but which since was deleted or revised (we're not sure which without a lot of research).
Victor's spell should break down as follows:
Assume the target has Superb Endurance (human maximum, more or less), and has rolled the best possible on its defense (+4) but without bringing any aspects to boost it beyond that. That's 9 shifts to overcome right there.
This means the target also has a stress track of length 4, two mild consequence slots (due to the extra one that comes with Superb Endurance), one moderate, one severe, and may choose to use its extreme slot as well.
Natural thresholds won't matter like they might with a targeted evocation or whatnot because the spell likely uses a component that opens a direct conduit to the target (fresh blood or hair; a true name). No defensive benefit there.
It's possible that the target could be magically warded specifically against this sort of thing, but except for Harry, Victor would have no expectation of a warded target, so that doesn't enter into things (and it's possible that the interpretation of magic instead points at the direct conduit getting around that sort of thing too; might depend on what kind of warding magic is brought to bear).
There's also no expectation that the target has some sort of armor or other defense that might apply in the way of supernatural Toughness powers.
The attack stress the spell deals in a single stroke has to beat the best defense (9), all of the consequence slots (2+2+4+6+8 = 22), and then end up with a stress amount that will land somewhere higher than the highest possible box, forcing a taken out result (5, when dealing with a stress track 4 boxes long). 9 + 22 + 5 = 36.
So that's where I'd set the Sure Thing complexity... for a mortal target with no supernatural defensive juju going its way.
I'll double-check with the team to make sure I've summarized this correctly. If I haven't, I'll post another correction. If I have, I'll get it into the book as best as I can.