Tafsir of An-Najm 53:52

(And the people of Noah) is also a conjunction linked to (Ad). (From before)—meaning, from before the destruction of Ad and Thamud. The mention of "beforehand" is explicit because Noah, peace be upon him, is the second Adam, and his people were the first of the transgressors and the destroyed.

(Indeed, they were the most unjust and the most tyrannical)—that is, [more so] than the two groups [previously mentioned]. This is because they used to harm him and beat him until he could barely move. A man among them would take his son by the hand, walk with him toward Noah, and warn him, saying, "O my son, my father walked [to this place] with me when I was your age; beware of believing him." Thus, the old would die in disbelief, and the young would grow up according to their father’s injunction. They were not moved by his supplication, even though he called them for a thousand years less fifty years.

It is also said that the pronoun in (Indeed, they were) refers to all those who preceded: Ad, Thamud, and the people of Noah—meaning they were more unjust and more tyrannical than Quraish. In this, there is a consolation for the Prophet, peace and blessings be upon him, which is not hidden.

Regarding (they), it is permissible for it to be an emphasis for the attached pronoun, and it is permissible for it to be a fasl (pronoun of separation), as it occurs between a definite noun and the superlative form. The omission of the object of comparison when it serves as the predicate of kana follows the same rule as the predicate of the subject (mubtada'), and its omission therein is eloquent; thus, it is the same for the predicate of kana.