User blog comment:Flamesword300/inuyasha,sesshomaru weilding the whole shikon jewl/@comment-121.245.36.196-20120126205733

The jewel will have no effect on Sesshomaru. His demonic aura is naturally complete and as such the shikon jewel is a useless trinket from Sesshomaru's point of view(as he told Kagura, saying that he had no use for the jewel). In fact the only time he did possess a jewel shard (when he used a human arm to wield tessaiga), it had no noticeable effect on him.

On Inuyasha, if its just a shard, not the whole jewel itself , he'll simply become the berserk pseudo-full yokai that we are all familiar with. However, the whole jewel will transform him into a form more similar to his father and brother's.