4. Dogo Argentino
The dogo Argentino is a big-game hunting breed that was developed in the 1920s in Argentina to hunt wild boar and puma. The breed’s founding stock came from the now extinct and highly aggressive Cordoba fighting dog, but many other breeds went into the genetic makeup as well in an effort to eliminate aggression. The result is a generally well-balanced, powerful and protective dog that gets along well with people and is very affectionate with family. However, their size, intelligence, prey drive and energy needs make this dog potentially dangerous without training.