The French Connection (1971) and The French Connection II (1975)

These two touchstones of 70's cinema are far more arty and weird
than expected and the underappreciated, divisive sequel is
punishingly challenging. It's rare for any actor to shine as
brightly as Gene Hackman but even rarer for a sequel to a
multi-Oscar winning film to replace the director with someone
equally exciting, going from William Friedkin to John
Frankenheimer, both at their peaks. It maybe ground zero for the
cynical modern cop drama but are as were as artistically dazzling
as these films.