Ulquiorra
Cifer

Ulquiorra Cifer is the fourth Espada, Aizen's most loyal instrument, and the show's coldest argument about what a heart is. He first appears in Karakura Town to evaluate Ichigo and decides he is trash not worth killing. His analysis is always delivered in the same flat voice, green tear lines running down a white face, hands in his pockets while he decides whether something is worth existing.

Aizen sends him to collect Orihime Inoue, and the abduction is pure Ulquiorra: no violence, just a demonstration of what will happen to her friends if she refuses. As her jailer in Las Noches he brings her food, repeats Aizen's orders, and gets visibly unsettled by exactly one thing, her insistence that hearts live in the people who care about you rather than in the chest. When she slaps him, he does not understand why she is not afraid.

His two fights with Ichigo end the Hueco Mundo arc. The first is an execution: a Cero through the chest, delivered almost as a mercy. In the rematch above the dome he unveils Segunda Etapa, the second release no other Espada has, and beats Ichigo to actual death, which summons the horned Hollow form that tears Ulquiorra apart in turn. His ending is the point of his whole character. Dissolving into ash, he reaches toward Orihime and asks if he frightens her, and she says no and reaches back. The hand crumbles before she can take it. In his last seconds, the thing in his palm is what he finally recognizes as a heart.