I've had the thought that Odium was able to overcome and splinter other shards because he hadn't Invested in any one place, meaning that he has more, if only slightly, power than other shards.
However, if he came against a being wielding multiple shards, he may have more problems. While Sazed is more Invested in Scadrial than most shards, he also has the power of two shards, neither of which would much like being splintered. Unless Odium has access to more power than two shards, he may have a bad time if he attacks Scadrial.
Just as an aside, if Ati had been a meaner fellow, like Rayse, and not invested in Scadrial, would he have gone on a Splintering rampage like Odium?