"Then the end of those who did evil," meaning: they associated partners with Allah, "was the worst," meaning: Hellfire, "for they denied the verses of Allah," meaning: because they denied them.
Muhammad said: Whoever recites "aqibatu" (the end) in the nominative case makes "as-su'a" (the worst) the predicate of "kana" (was). The origin of the word is the feminine form of "al-su'" (evil). The poet said: