In 2005, Kross came to the attention of Detlev Buck through his daughter, Bernadette, and he auditioned for "Tough Enough" ("Knallhart"); Buck hired Kross to play the lead, a 15-year-old boy who moves with his mother from a rich neighborhood of Berlin (Zehlendorf) to the Neukölln area, known at the time for its high number of Turkish immigrants and high crime level. Kross not only won praise at Berlinale in 2006, but also won Best Actor in Nuremberg at the 11th Filmfestival Türkei/Deutschland.