Surah Al-Naas (Chapter 114) is the surah that ends with the word "Mankind." The name Al-Naas itself means "Mankind" or "The People." The final verse of this surah (114:6) reads: "Min al-jinnati wan-naas" - "From among the jinn and mankind." The very last word of this verse, and therefore of the entire surah, is "an-naas" (mankind).
Surah Al-Naas is the last chapter of the Qur'an and is one of the two Mu'awwidhatain (the two surahs of seeking refuge), alongside Surah Al-Falaq. It is a prayer seeking Allah's protection from the whispers of the retreating whisperer (al-waswas al-khannas) who whispers evil into the hearts of mankind.
The other surahs listed do not end with the word "mankind." Al-Zalzalah (The Earthquake) ends with a reference to deeds, Al-Takathur (The Rivalry in Worldly Increase) ends with a reference to being questioned about blessings, and Al-Falaq (The Daybreak) ends with a reference to the envious.
