Sickle was a Russian circus performer along with his conjoined twin brother Mister Hammer and the two split up after an argument. Sickle worked for Penguin while his brother; Mister Hammer works for Joker in Batman: Arkham City. After the main story ended, both Sickle and Mister Hammer had forgiven each other, and wish to be reconnected.
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 Russian circus. They got into an argument and split up, joining separate factions in Arkham City.
Born in a small Siberian village, Sickle was conjoined to his twin Mr. Hammer upon birth, causing their father to resent his hideous children. Abandoning the twins at a local circus, they quickly became known for their brutality and authenticity, referred to as the Abramovici Twins. Their reputation soon attracted the attention of the Joker, who sent Harley Quinn to negotiate the twins to be in his gang, but was forced to kill the circus owner when he refused the offer.
While watching his new recruits battle Batman, Joker realized that it would be an advantage to have them separated, and hired Dr. Thomas Elliot to perform the operation. As he wanted a "right-hand man", Joker kept Hammer and had Quinn dispose of Sickle, leaving him at the Iceberg Lounge as a present for the Penguin. Cobblepot soon employed Sickle into his own gang out of their resentment for the clown. After Arkham City was constructed, Penguin's entire crew was trapped inside, including Sickle. Sickle was later seen as a juror in Two-Face's trial against the Joker, voting him guilty for separating him from his brother.
Batman: Arkham City
Sickle first appears in the Cyrus Pinkney Institute for Natural History, in the Gladiator Room right after Officer Best is shot by the Penguin. Sickle holds Officer Forrester by the neck while Penguin addresses Batman and starts the "initiation". Sickle, Penguin and the other henchmen leave Batman to die.
Batman survives, and follows Penguin. Sickle has separated from his leader at this stage. He appears once more in the War Room. As Batman attempts to rescue Mr. Freeze, Sickle bursts through a wall with a number of henchmen, they fight with Batman, who once again triumphs, knocking them all unconscious.
Sickle is last seen reconciling with his brother, Mister Hammer, and talking to him in the Steel Mill. They consider getting stitched together so they can be together again.
Sickle has "✰" tattoo, showing that he has origins from Russia. Also his brother, Mister Hammer wields a large sledgehammer. Sickle himself wields a large sickle. Hammer + Sickle = ☭.
Sickle is seen in the "Joker's Carnival" challenge map, along with Mister Hammer.
He needs 50 hits to take him down, as does his brother. If you do so uninterrupted you can get the 50X achievement by fighting him alone.
The fact that his brother wields a hammer, and he a sickle, is a reference to the Soviet flag, which has a hammer and a sickle crossing it. This is a reference to how the two are Russian.