Yo, "el Vaquilla" (1985), directed by José Antonio de la Loma, is a seminal "Cine Quinqui" film documenting the gritty, true-life story of notorious juvenile delinquent Juan José Moreno Cuenca. The film portrays his upbringing in Barcelona's slums and rapid descent into crime, featuring a soundtrack by Los Chichos and starring Raúl García Losada. Read the full film details at Filmaffinity . The Gypsy (1985) - IMDb
De la Loma had previously directed the 1979 film Perros Callejeros (Street Dogs), which featured a character inspired by El Vaquilla . However, Yo, "El Vaquilla" is the authorized, direct biopic. Moreno Cuenca plays himself . This is not method acting; it is a documentary of a life spiraling out of control. The film follows his trajectory from petty theft to violent robberies, prison breaks (he famously escaped from the Barcelona Children’s Jail in 1979), and his eventual romanticization by the media as a "romantic rebel"—a label the film fiercely critiques.
Be careful to distinguish this from another 1985 Spanish film simply titled "La Vaquilla" (The Heifer), which is a comedy by Luis García Berlanga set during the Spanish Civil War.