The Rebel.

"Poliziotti solitudine e rabbia" or "Ein Mann namens Venedig" (A Man called Venice), as it was called in Germany, is an Italian-German crime drama co-production from 1979, filmed mainly in the snowy winter of bleak West-Berlin. Italian cop Nick, played by gangster movie veteran Maurizio Merli, goes to Berlin to find the head of an International European blackmailing gang who has murdered several people. He investigates undercover as a contract killer for the gangsters, but of course becomes immediately the target of his enemies and has to fight hard to save his life...