How do you say enemy in Japanese?
— 敵 (teki, kataki)

Generic synonyms for enemy in Japanese
people国民 (こくみん, kokumin); 民族 (みんぞく, minzoku); 人民 (じんみん, jinmin)
Antonyms for enemy in Japanese
friend友達 (ともだち, tomodachi); 友人 (ゆうじん, yūjin)