From LEGO Batman Wiki
Mr. Zsasz is one of Batman's most perilous and frequently-faced foes who defeats without being provoked, usually with his weapon of choice, a knife. He is also regularly sent to Arkham Asylum due to the fact that he is a psychotic sociopath. Mr. Zsasz appears on the Nintendo D.S. version of LEGO Batman: The Videogame as one of the villains in Villain Hunt. He is play-able after you find him and pay 400,000 LEGO-studs.