Mosco de la Merced (Juan Valdez Valentino) (June 26, 1964 – August 19, 2024) was a Mexican Luchador or professional wrestler, best known for his time in Asistencia Asesoría y Administración (AAA) where he was a part of Los Vipers for many years.

[1] After the UWA closed Valentino began working for Asistencia Asesoría y Administración (AAA), one of Mexico's largest wrestling promotions.

[7] This allowed Mosco de la Merced (II) and Fuerza Guerrera to remain tag team champions and also fill the void in Los Vipers.

[6] On June 7, 1998 Mosco de la Merced and Fuerza Guerrera lost the tag team title to Perro Aguayo and Perro Aguayo, Jr.[6] On August 23, 1998 Mosco de la Merced, Maniaco, Psicosis II and Histeriateamed up to participate in a tournament for the vacant Mexican National Atómicos Championship, representing Los Vipers.

Mosco de la Merced was able to escape the cage and thus save his mask, although his fellow Viper Maniaco was less fortunate and was unmasked.

During mid-2004 Los Vipers, in this case Mosco, Histeria and Psicosis II became involved in a feud with Heavy Metal, El Intocable and Zorro that led to a Steel Cage match at Verano de Escandalo 2004 in which the last man in the cage would be unmasked or have his hair shaved off.

This time Mosco de la Merced was the last man in the ring and was forced to unmask per Lucha libre traditions.