Thaumaturgy and Ritual have no upper limit to how much power you can put in one working, right? That means that a really unscrupulous disruption ritualist -say, a red court vampire- could start sacrificing people to up complexity. Every sacrifice adds a whopping 22 shifts to the effect. And there is no time limit; you could keep sacrificing people to the same ritual place you set up for years... until you build up and unleash a 20000-shift curse that obliterates an entire bloodline or something.
Alternatively, an equally unscrupulous but smarter ritualist could tie up a hundred people in his den. Then he could ritually bleed or torture them one by one for one exchange, inflicting small amounts of pain each time - a mild consequence. By the time he came back to torture the first victim, an hour (couple of scenes) would have passed, allowing them to recover (the consequence to heal) and the circle to start anew. Doing it for a few hours each day and then having some helpers water and feed the captives would allow thousands of shifts a day.
To call up the power once the ritual complexity is amassed, the caster, even if we assume 1 shift per exchange and that and exchange is a few seconds, would need an hour for 1000 shifts. If he has a +2 control focus, he could safely call 3000 shifts in an hour. If he has a +5 focus, requiring a dedicated ritualist of at least feet in the water level (-5 refresh), he could call 6000 shifts.
Let's see actual numbers. Assuming zone progression is linear and you can't get bigger zones after a while;
An average rocket or smart bomb is weapons 8-10 for an entire zone, equivalent to 12 shifts of ritual-easily within the abilities of any ritualist without sacrifice.
An average cruise missile or big bomb would be weapons 10-12 for five zones, taking out a medium building. That's 22 shifts, the power of a single sacrifice.
A small nuclear explosion is weapons 20 for 500 zones, taking out dozens of city blocks. That's 1000 shifts or so, the work of a single day of preparation in a major working.
A greater nuke that takes out an entire major city is weapons 40 for 20.000 zones. That's about 40.000 shifts, meaning it can be acheived by a dedicated ritualist by sacrificing 2.000 people or torturing 100 people for two months, and then spending 8 hours to call up the humongous amount of energy.
A supernatural organization taking advantage of third-world countries could easily get that many humans to sacrifice or torture over time. A single practitioner could take advantage of circumstances, cause events to run in his favor to, say, have a couple thousand spirits at hand to devour and bring about that level of power, or make a very special arcane drug and then sell it, not only to finace his work but also link the victims of the drug to his ritual. 1000 junkies stoned for a week (several consequences per day each) could give that much power.
How many evil ritualists are there in the world again? Better hope nobody does anything stupid like disband the only governing body policing the use of magic or the consequences might make a major nuclear exchange seem like a better idea...