"Cole Younger, Gunfighter" is a remake of "The Desperado"...which is odd since the first film was made only four years earlier. Also, despite the title mentioning the real-life criminal, Cole Younger, it is a fictional movie.
The story begins in the South just after the Civil War. In this Hollywood version of history, the South was being cruelly run by evil Carpetbaggers and Bluebellies. Carpetbaggers was a nickname for Northerners who moved to the South following the war in order to exploit the Southerners. Bluebellies were Union soldiers stationed in the South. The problem is that although MANY films of the 20th century talk about the scourge of these two groups, this really isn't very accurate. Although surely SOME of the troops and Carpetbaggers exploited the people and were jerks, this is NOT the norm. What WAS the norm is that many Southern men felt disenfranchised...and joined the KKK in order to retake power and keep black citizens from power. I don't want to talk much more about this, but it is a common myth in movies.
In this story, two Southern men are randomly picked out during a peaceful meeting which had nothing to do with politics or hate. The two men are cruelly beaten in order to get them to confess to crimes against the Reconstruction government (i.e., the military leaders appointed to run the various ex-Confederate states). The pair are beaten badly...but one manages to stop his attacker and he ends up beating the Bluebelly. Now Kit and Frank (James Best and Jan Merlin) are on the run from the law and eventually meet up with the bandit, Cole Younger (Frank Lovejoy). Frank tries to capture Younger for the reward money....and Kit beats the snot out of him. As Frank runs off, he threatens to 'get you both'! Younger is worried that not killing Frank will come back to haunt him. And, because Kit stays with Younger, he finds that he is now a wanted man. What's next? Well, apart from a lot of shooting, you should just see the movie.
If you realize it's almost all fiction and you don't mind its historical inaccuracies, then you are left with a pretty good film with some very good acting.
Sadly, this was Frank Lovejoy's last film....as he had a fatal heart attack at age 50. He's quite good in the film...even if he lacks any sort of Southern accent.