((LATIN ALERT: The nouns and adjectives should agree in case, number, and gender. Assuming you meant to say "bad little horse" Equus is in the accusative case (probably not the case you want to use since accusative usually requires an action by a subject) while minor and malus are in the masculine nominative case. It should be Equus Malus Minor, word order really doesn't matter (or if you want to be fancy you could use vocative, Eque Male Minor "O bad little horse!")))