I have to throw in my two cents here... if his element was DEATH, he wouldn't need to FIGHT anyone. He'd just have to snap his fingers and BOOM... all his enemies are DEAD. He wouldn't have needed Sora to overthrow the Organization, because he'd be able to kill them HIMSELF. Thus... his element is not death, and it cannot BE death, because no game developer would be utterly STUPID enough to make such an overpowered adversary.
As for the scythe, has anyone who thinks that his element of death actually SEEN his title? "The Graceful Assassin". Now, given that he has a scythe, if his element was death, wouldn't they have called him something like "The Graceful REAPER"???