Sickle

Sickle, also referred as Captain Abramovici, is The Penguin's one armed lieutenant in his army. He was mentioned to be with his conjoined twin, Mister Hammer, performing at a Soviet Union circus. Yet, they got in a huge argument and broke up, literally. They moved to Gotham for some unknown reason, and became criminals.

Batman: Arkham City
Sickle is first seen before The Penguin unleashes all of the thugs on Batman, holding a cop by the neck. Sickle next appears when Batman faces him, along with a bunch of Penguin thugs. Sickle is last seen reconciling with Mister Hammer.