After the American Civil War, ex-Union soldier Keoma Shannon, part-Indian and part-white, returns to his home town to find his half-brothers in alliance with a petty tyrant named Caldwell. Caldwell and his gang rule over the town with an iron fist. With the help of his father and George, an old Black friend, he vows revenge. Keoma also shows compassion when he saves a pregnant woman from a group sent by Caldwell's group to be quarantined in a mine camp full of plague victims. Keoma is constantly visited by the apparition of an older woman ("The Witch") who saved him during the massacre of an Indian camp.
While participating in the filming of 21 Hours at Munich, Franco Nero was approached by his longtime friend and collaborator Enzo G. Castellari and producer Manolo Bolognini on the proposition of appearing in a Spaghetti Western, despite dwindling demand for films of that genre. At the time, no stories or scripts had been written - Nero, Castellari and Bolognini did, however, decide to name their pet project Keoma, which was a Native American name that, according to Bolognini, meant 'freedom' (in reality, the name means 'far away').
Keoma was reportedly planned as a sequel to Sergio Corbucci's Django, which Bolognini co-produced. The original treatment was written by actor George Eastman (Luigi Montefiori) and developed into a script by Mino Roli and Nico Ducci, neither of whom were experienced writers of Spaghetti Westerns. Roli and Ducci's screenplay arrived three days after shooting began and was quickly thrown out by Castellari and Nero, unanimously believing that it was not appropriate for a Western. Castellari proceeded to rewrite the script on a daily basis throughout filming, taking suggestions from cast and crew members, as well as being influenced by the works of Shakespeare and Sam Peckinpah, among other sources. Most of the dialogue as it appears in the film was written by actor John Loffredo, although Nero also contributed a substantial amount of his own lines, including his final exchange with "The Witch".
The film was shot over a period of eight weeks, with most principal photography being done at the Elios Studios in Rome, where Corbucci had previously filmed Django. The studio's set was in dire need of repair, which made it easier for Castellari to film as they did not have to redress the sets. The film was also shot on location at Lago di Camposecco.
Keoma premièred in 1976, and was considered a mild success in Italy at the time. The film grossed a total of 1,571,995,000 Italian lira in Italy on its theatrical release.
Some countries promoted the film as a Django film. These included France (Django Rides Again) and Germany (Django's Great Return). In the UK, the film was released in 1977 by Intercontinental Films as The Violent Breed, while Vadib Productions released the film in the United States as Keoma the Avenger in 1978. Spanish promotion for the film lists Sergio Leone as a producer which he is not credited with anywhere else.
In a contemporary review, the Monthly Film Bulletin reviewed a dubbed 85 minute version of the film. The review noted that the film was "too severely cut to follow its plot easily let alone its multiple Freudian undercurrents", but stated that "visually it has many impressive if conventional aspects", noting the introduction and various flash back scenes. The review also praised Franco Nero as "endlessly enjoyable" and concluded that Keoma "is an effective reminder that the Italian Western was always formally more intriguing than its critics would have one believe."
In a retrospective review, AllMovie gave the film four stars out of five, and referred to the film as one of the "finest efforts" of the Spaghetti Western genre. The review noted that the "plentiful gunplay is choreographed with balletic grandeur, the camera work is sweeping and lyrical" and Luigi Montefiore's script "is heavy with spiritual metaphor while still adhering to established Western tenets." AllMovie also commented on the score as "the film's sole drawback", finding it "often tone-deaf".