The Boondock Saints (1999)

The "Boondock Saints" are two working-class brothers of Irish descent living in Boston, Connor (Sean Patrick Flanery) and Murphy McManus (Norman Reedus). Though they at first seem to be laid-back, lovable pranksters, the brothers have a strong sense of right and wrong and won't back down in a fight. An FBI agent (Willem Dafoe) becomes involved when the brothers start leaving bodies behind them, though he quickly comes to like the criminals he's tracking. With the incompetant help of their bumbling friend Rocco (David Della Rocco) (who also works as an errand-boy for the mob), the brothers begin targeting the "evil men" of Boston, eventually getting help from the mysterious "Il Duce" (Billy Connolly), who has secrets of his own regarding the brothers.