This is what I was referring to. (The Big Giant Head in Kaladin's dream also says it.) It's not just that Odium is dangerous because of who holds it, but the Shard itself is somehow the worst of the sixteen. What I was asking is, how can that be, given what we've seen of Ruin? It's all very well to say "hate is worse than destruction," or that it matters that Rayese is an cremhole while Ati used to be a nice guy; that's just theory. In practice, what could Odium actually do, in accordance with his Intent, that would be "worse" than what we know Ruin would have done?
Perhaps "in the blink of an eye" is an exaggeration, but The Hero of Ages makes it clear that if Ruin had found the atium, he would have destroyed the planet "quickly." Bang, earth shattering kaboom, everybody dead. I'd rather be attacked by Voidbringers than have the world end all at once, I think.
I admittedly wasn't thinking of that. So, if Odium "wants" to end Roshar like we saw in Daliner's vision, why doesn't he? Unlike Ruin he doesn't have another god stopping him, and he isn't missing part of his power. So what's he waiting for?
Now I concede that Odium does indeed seem to have it in for the entire Cosmere; hence the theory about the Voidbringers becoming a space race that commits genocide on every planet they find. But, again, given what we saw in The Hero of Ages, Ruin could have wrecked up the Cosmere a lot more efficiently than that. Odium may be Crayak, but Ruin is Galactus.
(Heh, I just realized that the Voidbringers even look kind of like Howlers. "Creatures of ash and flame" indeed. )