Natasha - A New Mission

Before SHIELD, Natasha and Clint tried to kill each other.
Natasha works for the KGB, hunting down HYDRA traitors in the system. When she's assigned a job at the Russian ballet, she battles memories of her past she never wanted to face again.
Clint is a fugitive, framed by his brother for attempted murder. Some guy in a suit shows up, Special Agent Phil Coulson, representing a government division Clint can't pronounce, with the offer of a fresh start and Clint finds himself a brand new recruit of SHIELD.
Then there was Budapest where no amount of training could prepare them for the choices they would be forced to make.

NOTE: This is largely unedited, so please excuse errors, plot holes, etc.