Hi guys, i've got two theories (not mutually exclusive) for why Odium can Splinter other Shards.
1.Odium is more powerful than the other Shards.
While i've constantly seen references to Adonalsium shattering into sixteen pieces, i don't think i've ever heard mention ofthose pieces being equal in size. Maybe when the Vessels were taking the power Rayse took a bigger chunk of Mr A's corpse. This would enable him to overpower other Shards and kill them whilst still having enough power to survive.
2.Odium's Intent causes the Splintering
Odium means extreme hatred and dislike, and also the state of being hated. Hate also causes people to turn away from one another, to divide. What if this applies on a Shardic level as well?
What if Odium can infect a Shard with hatred? Self hatred to be exact. Similar to a virus turning a body's immune system against itself, what if it does the same to the Shard, which causes it to
fracture and essentially self-splinter. It would also make sense why we haven't seen other Shards do this. For example, Dominion and Devotion, while seemingly different are in the end both about unity. They couldn't Splinter others even if they tried. The same goes for Preservation, Honor and probably Cultivation. This gives Odium a major advantage. Ruin may be able to do it but remember that he was imprisoned by Preservation for millenia and couldn't find enough opportunity to practise. Also, while Rayse was a nasty fellow even before becoming Odium and thus naturally inclined to find a way to kill the others, Ati was supposedly a pretty nice guy. It wouldn't be in his nature to practise this.
That's it guys, could be on to something or it could be a load of crem
Thanks anyway, interested to hear what you think.