The answer to Legend's dilemma is pretty clear. He is wrong about base delta zeroes not being able to destroy all lifeforms - Zenwolf gave plenty of sources saying exactly the opposite - so he just tries to dismiss those sources because another one seems to contradict them. Of course, that contradiction makes the assumption that the superlaser in question > a base delta zero, and that this one source outweighs several others, but let's run with these stupid holes in his argument:
Vitiate's ritual kills everyone, but its environmental damage is disproportionately small. Clearly it has some special targeting and isn't just doing it via a big explosion. We are, however, debating raw power in this tangent. The energy needed to kill/vaporize/etc. every human on Earth, for example, is vastly smaller than that needed to turn the surface to molten slag. This means that Vitiate's Ziost ritual is less energetic even though it [allegedly] kills more people. Legend just decided to use death count as the sole indicator of destructive output, even though slagging the surface would actually require far more. It is [assuming the above] more effective at killing people because it focuses on that, but it doesn't compare to Sidious's Storms in raw destruction. 👆