Blood-Stained Black Rabbit

Japanese name:	血染めの黒ウサギ
Nickname:	B-Rabbit

Blood-Stained Black Rabbit is arguably the most powerful Chain within the universe of Pandora Hearts.
He is capable of summoning numerous bladed chain links that can dismember human bodies as well as cut through nearly any substance which they come into contact with. This includes the Chains which surround the world and prevent Earth from being engulfed by the Abyss. His powers also include the ability to destroy anything he wishes by turning it into sand.

SpoilerAlice was originally thought to be B-Rabbit, however, it was revealed that Oz Vessalius, is in fact the true B-Rabbit, and Alice is only a physical manifestation as her soul joined with Oz's body, taking his power, to prevent him from causing any more harm

Source: Pandora Hearts Wikia

http://pandorahearts.wikia.com/wiki/Alice