There is a character named Carolina in "Once Upon a Time in Mexico," played by Salma Hayek. In the film, Carolina is a retired FBI agent who has a romantic history with El Mariachi. She is approached by Sands, a CIA agent played by Johnny Depp, to help him stop a coup led by a Mexican drug lord.

Carolina is shown to be highly intelligent and resourceful, with a strong sense of justice and a desire to make a difference. She is also fiercely independent, choosing to live off the grid in a remote village in Mexico. However, her love for El Mariachi and her desire to help stop the coup lead her to become involved in the dangerous mission.

Throughout the film, Carolina displays a combination of toughness and vulnerability, showcasing her ability to handle herself in dangerous situations while also revealing her emotional attachment to El Mariachi. She also has a significant impact on the plot of the film, playing a key role in helping Sands and El Mariachi stop the coup.

Overall, Carolina is a complex and well-rounded character who adds depth and emotional weight to the film. Salma Hayek's performance as Carolina has been praised for its nuance and intensity, helping to make her one of the most memorable characters in the movie.