Mississippi Burning

A 1988 film very based on the investigation of the murders of three civil rights activists in Mississippi. Two FBI officers must work their way through a hotbed of county-wide lies and deceit, with little support from citizens, to solve the murders.

Tropes used in Mississippi Burning include:

Badass Bookworm: Agent Ward.
By-The-Book Cop: Agent Ward, until Mrs. Pell's beating convinces him that playing by the book won't lead to justice.
Complete Monster: The KKK members viciously attacks black people hangin some of 'em and setting their homes on fire. One of 'em even arrives to almost beat the pulp out of his own wife after she says everything to FBI.
Corrupt Hick
Cowboy Cop: Agent Anderson.
Dangerously Close Shave: The FBI agent played by Gene Hackman intimidates a KKK member who was getting a shave by replacing the barber.
Deep South
Domestic Abuse: Deputy Pell beats up his wife when he finds out that she has helped the FBI.
Driven to Suicide: The Mayor
False-Flag Operation
Grey and Black Morality: Toward the end, once the FBI adopts Anderson's preferred tactics.
Groin Attack: Anderson inflicts one on a Klansman.
High Heel Face Turn: Deputy Pell's wife informs on the KKK. She gets beaten up for it, but survives.
It's Personal: Agent Anderson after Mrs. Pell, to whom he was attracted, is beaten by the KKK for being an informant.
Jurisdiction Friction: Justified, because many of the cops are in league with the Ku Klux Klan
Kangaroo Court: Several Klansmen are tried for arson in a local court that has no intention of imposing any real punishment for the crime.
Mighty Whitey: The two FBI agents who come in to speak on the behalf of those oppressed and end up bringing national attention to the situation in the South. In truth, the civil rights movement in the area was already thriving and FBI agents investigated the Klan only under heavy pressure from the President.
Nice Job Breaking It, Hero: Many of Ward's well-intentioned, by-the-book actions early in the film make the white population of Jessup County feel angry and threatened, which only makes matters worse for the black community. Anderson calls him out on this, to no avail (at least initially).
Politically-Correct History: FBI agents as heroes to the Civil Rights Movement. As most historians know, J. Edgar Hoover was no fan of the movement in Real Life and the agency in fact took several notable measures to undermine and sabotage the movement (although individual agents as depicted here, of course, may have had differing views on the situation).
Scary Black Man: The FBI brings in a professional Scary Black Man to intimidate the corrupt mayor into revealing who committed a hate crime.
The Sheriff: Jessup County's sheriff does not appreciate FBI interference in his county's affairs, since he's in league with the Klan himself.
Stoic Spectacles: Agent Ward.
Very Loosely Based on a True Story
Villain with Good Publicity: The KKK appears to be this among the white citizens of Jessup County, although Mrs. Pell probably isn't the only one who doesn't like the violence but is too frightened to speak up.