Abattoir (real name Arnold Etchison) is a DC Comics character appearing as an enemy of Batman. He is a serial killer who first appeared in Jaunary 1991 in Issue #625 of Detective Comics.
A serial killer who was convinced that his family was evil, Arnold Etchison believed that he absorbed something of their life force when he killed them. He was apprehended and incarcerated in Arkham Asylum, which he escaped from several times, always being returned by Batman. His final escape came when Bane set all the inmates free in the Knightfall storyline, after which Etchison went on to kill several more members of his family.
Eventually he was tracked down by Jean Paul Valley (better known as Azrael), who was acting as Batman at the time, unbeknownst to Etchinson. Valley chased him into a refinery and nearly knocked him into a vat of molten metal. Abattoir was hanging from a chain above, barely able to hold on, but Valley, immobilized in a crisis of conscience, allowed him to fall to his death, to Robin's horror. Since Abattoir was holding a relative, Graham Etchinson, inside a secret, hidden torture chamber at an unknown location, Valley indirectly condemned that prisoner to death—though he was unaware of this until informed by Commissioner Gordon. This scenario was the main factor in Bruce Wayne deciding to reclaim the role of Batman, when considering retirement.
Abattoir returned as a ghost (during a brief period of increased supernatural activity, worldwide), to torment the original Batman (Bruce Wayne) using Valley's Batman-armor, but Batman proved much less susceptible to psychological assault than his substitute. Batman tricked Abattoir's ghost into abandoning the armor and his mission. (The ghost was attempting to cause his last remaining blood relative, a pregnant cousin, to miscarry and then he would possess the infant.)