Serpico
"Serpico" is a strong film with a bitter aftertaste. I really like the way Lumet shows us a hero, Frank Serpico, the police officer with honor. But "Serpico" is kinda depressive and pessimistic, because we can see Serpico got nothing, except justice, he got only a hate from his colleagues.
It was based on the true story of real hero, but, unfortunately, the system didn't change since 1972. And even after this film, corruption in the police still exists. Frank Serpico sacrificed his whole life (metaphorically like Jesus) for the little victory. And this is a victory of justice.