The Alfa squad is the secretive anti-terrorist unit of the FSB (former KGB). Their most notable mission during the Soviet period was the seizure of Amin's palace in Afghanistan in 1979 where a comparably small Alfa group (approximately 45) killed both the president and his elite guards (about 200). The most recent operation conducted by Alfa was the liberation of Moscow hostages and the killing of 49 well-armed guerrillas in the Moscow theatre siege of 2002. During the Soviet war in Afghanistan they were called "red devils" by the Mujaheddin.
It is also known that Alfa has never failed an operation (unlike its western analogues), and there were thousands of hostages rescued throughout its intense 25 year history.
In the latest Moscow hostage crisis there have been reported 129 hostages killed, but taking notice of the whole amount of all the hostages present in the theater, this number is roughly 16%. Also, none of them died by the Alfa operatives' fire.
It should be noted, however that special forces units tasked with hostage rescue operations would consider an operation in which even a single hostage died to be a failed operation, regardless of the cause of death. The hostages killed in the Moscow theatre siege died as a result of the use of nerve toxins by Alfa operatives.